I'm driving the renowned heritage architect and prolific author around Canberra's inner south on a bright autumn morning to trace what remains of Malcolm Moir and Heather Sutherland, Canberra's 20^th century modern architectural power couple.

But on this highly desirable street of leafy trees and big blocks, we're too late. Watching builders put the finishing touches on a new house - fairly bland, the kind of thing that wouldn't be out of place in any well-to-do suburb in any non-descript Australian city - makes it feel like we've missed something by mere seconds.

Luckily, our adventure is not completely doomed. Although we arrive unannounced, owners of these remarkable houses invite us in and show us how spaces conjured up in pencil and ink decades ago still make living worthwhile today.

Nestled between edifices which represent new money or grand diplomatic ambition, behind the facades masking shallow design thinking, Moir and Sutherland's smart, intelligent and never overbearing homes stand as a reminder of what good architecture can do.

Freeman, an award-winning architect who served as president of the Royal Australian Institute of Architects' ACT chapter and chair of the territory's heritage council, has written many books on Australian architecture and had a long practice melding the old and the new. Freeman was awarded the medal of the Order of Australia in 2019 for service to architecture. He is also the preeminent expert on Australian woolsheds.

Thoroughly Modern: The Life + Times of Moir + Sutherland Architects is a richly illustrated sweep of Canberra's built and social history, a well-documented history of Malcolm Moir and Heather Sutherland's life together, working from home before it was popular and crafting a string of architectural achievements.

It's a story Freeman is perfectly placed to tell. A 1985 profile of Freeman in Vogue Living Australia said his "far-seeing eyes convey a certain dreaminess, but conceal a furious energy". Little has changed, even though Freeman is now into his 70s.

I meet Freeman at 3 Wilmot Crescent, a Depression-era home that has since been sympathetically and expertly extended. The house's owner is kind enough to let us explore the building, cared for and appreciated by a family who've come to be custodians of its history.

Inside the house is very different from its original scheme, Freeman tells me, but the outside remains mostly intact. Built with cream bricks, the original footprint of the Depression-era home is fairly modest. It shows big is not always best.

A solicitor, W.H.B. Dickson, engaged Moir in August 1936 to design the house, but it wasn't home for long. Dickson was declared bankrupt in 1940, probably fled to Goulburn and the house was sold to the British high commissioner. Colin Stewart, the late nationally recognised architect, bought the house in 1989 and sympathetically extended it.

A short stroll away is 43 Melbourne Avenue, the home Moir built for his family in 1936, and came to share with Sutherland. Moir's first wife and the mother of his two eldest children, Nance, died in late 1935. Alone and with two young children, Moir needed a hand. Sutherland came down from Sydney to help out, and a few months later they were married in Sydney, Canberra society none the wiser.

Standing at the foot of the drive, Freeman tells me the Moir family's apocryphal story. One so charming that even the reporter in me is not in a rush to check in case it isn't quite right.

In 1937, Freeman tells me, Marion Mahony Griffin, whose joint efforts with husband Walter clinched the international design competition for Australia's national city, came back to visit Canberra. (It was the trip she declared there was no reason the city could not be one of the world's most beautiful.)

The story goes like this: the family noticed an older woman standing out on the drive - just where Freeman and I are standing. She declared this house was her favourite building. There were two buildings that Walter Burley Griffin would have liked in Canberra, she said. This house and the Civic Theatre. Moir had designed both.

For an architect forging ahead in Canberra - a new city, a blank canvas - could there be a higher honour?

Malcolm Moir first arrived in Canberra in 1927 to join the Federal Capital Commission. With offices in Acton - buildings now absorbed into the Australian National University - the commission was tasked with designing a new capital. Moir joined the staff of architects, and worked on projects that included the Albert Hall and the Institute of Anatomy, which is now home to the Film and Sound Archive.

But the Depression hit hard, and the architects were retrenched. In these lean years, Moir took a work-for-the-dole job as a labourer, helping build the Manuka Pool. He then took a job as the manager of the Capitol Theatre, the landmark cinema in Manuka, and maintained a private architectural practice.

Then Moir's wife, Nance, died suddenly while she was visiting home in Sydney. Moir was left virtually by himself in Canberra with two young children, aged six and two.

Heather Sutherland, a friend of Moir's from their time at Sydney University's architecture school, arrived in Canberra in May 1936 to help. By November, they were married and the couple moved in to 43 Melbourne Avenue on Christmas Eve. It was their home and architectural studio for the better part of two decades.

As the city recovered - there was no surer sign than the opening of the Moir-designed and managed Civic Theatre on Mort Street in 1936 - the couple made the inner-south their canvas. Working across a landscape that became home to a who's who of the capital's most important people.

They were busy years. At 43 Melbourne Avenue, breakfast was served at 8am. Jobs followed at 9am, before Moir visited the Capitol Theatre at 11am and the Civic at noon. Lunch was taken at home before the house's architectural studio became a hive of activity until 6.30pm. Then Moir would go back to the theatres, not going to bed each night until after midnight when they closed.

Freeman's book tracks the number of building applications each year, the commissions and projects completed. Not content with managing two busy cinemas, Moir would have multiple projects on at any given time.

There were the embassies, including the US ambassador's residence, the radio studios, and the private houses and commissions outside Canberra. Keep an eye out for the Sutherland Apartments on Canberra Avenue, too.

But there's one street that sums up the Moir and Sutherland architectural vision of inter-war functionalism better than any other.

Looking at early pictures of Canberra has a discombobulating effect. Little brick houses are set on enormous blocks. The horizon is not obscured by trees and hastily built apartment towers.

This is what early pictures of Evans Crescent show. Four distinctly modern houses in a row on a street hewn from a paddock. No wonder Freeman and I took a few wrong turns before unexpectedly turning up next to these buildings, now nestled between trees and decidedly non-modern homes. Stopping the car, the sound of work carrying on a new large-scale apartment development across the street hits us. Not much is left to stand still in a young city.

Completed in 1940, the Evans Crescent Housing precinct in Griffith was not designed in unison. Instead, the houses were, as this paper put it, linked by their "character and colour". Moir and Sutherland designed five of the houses, while Kenneth Oliphant, Canberra's first private architect, designed another - since drastically renovated.

Heather Sutherland was hands on with her clients. She regularly stopped in at Denman Street, Yarralumla, then on the fringes of Canberra, where a trailblazing woman was establishing her home - away from society's peering, conservative and judgmental eyes.

June Hyett Barnett, one of Australia's early female diplomats, would share the home, designed by Sutherland in 1953, with her partner Kay Keightley for close to 50 years. (Barnett was called before the Petrov royal commission in 1954, but refused to identify the Communist operator who had tried to suborn her when she was an External Affairs Department cadet; ASIO eventually lost interest.)

The Yarralumla house, however, is a project marked with sadness. Sutherland was on her way to visit the site, still in its early stages, when she was killed instantly by a Yarralumla Brickworks truck on Adelaide Avenue. Malcolm Moir's life was again marked by tragedy.

When Freeman surveyed the Moir and Sutherland buildings in the late 1990s, he didn't get past the nature strip at June Barnett's house. When we pull up to see it, Freeman can't resist knocking on the door.

It's a fairly strange house call: Hello, I'm an architect and this is a journalist and we'd like to look at your home. But the owners, who bought the house from June when she went into aged care, are gracious with their time and happy to invite us in.

Soon, the original plans are spread out on a table. Heather Sutherland's signature can be seen on the yellowed paper and felt in the shape of the room.

It's a similar story in Turner, where Freeman calls in unannounced on the owners of another Moir and Sutherland house, who helped out with material for the book. The house has been carefully maintained. There is a reverence you can feel stepping over the threshold for the house's fabric and meaning.

Moir kept working for a time after Sutherland's death. Neville Ward and Ian Slater, whose own architectural feats in Canberra are notable, became partners in the architectural practice, which moved from Melbourne Avenue to Endeavour House. Moir married Delitia Eleanor Harrington in 1955, another friend from his days at Sydney University. Moir's son Ian, then 21, was best man.

After some more good years - of architecture, movie-showing and travel - Malcolm Moir died in 1971. The Canberra Times said Moir was one of the city's better-known early residents, a cinema manager, architect and ACT advisory councillor - in that order. Moir's architectural firm was swallowed up by a larger Melbourne practice, leaving just the buildings and rich archive behind.

A whistle-stop tour of Moir and Sutherland buildings now inevitably reveals more has been lost than has survived. Freeman says the ACT Heritage Council could have been more alert to the situation.

"There's only two or three houses that are now Moir houses that are being kept intact. Pretty much all of the others are going. That's partly to do with a very, very rich economy that we've got now, which is quite different to what was happening in the '50s and the '60s - but sad, I think," Freeman says over a coffee after the journey.

"We were lucky, I think, today to actually talk to people who absolutely love their houses. Not only the houses, but the whole story that went behind them, with them, you know. They were very moving, I thought."

Freeman was chair of the territory's heritage council for three years and had to fight plenty of his own battles. (Some might remember the controversy over the proposed redevelopment of the bowling club on Hobart Avenue.)

"It was a very, very difficult job because you were always confronted by developers, by legal people, who are determined to actually make sure that their clients got what they wanted. It never was [a heritage listing]. How often do you get a solicitor standing up for a heritage place? It happens, but it's very rare."

When Moir was campaigning for newly established federal seat of Canberra as the Liberal candidate in June 1949, he said he saw well-designed apartments - ones that did not detract from the landscape - as the pathway for the capital's young people to have a place of their own. What would Moir have made of a skyline of high-rises marked out across the Limestone Plains, in a city where fewer people can afford to buy?

There was a concern for legacy, making sure there was a place for people in this city. Moir once declared that Canberra was a monument to the past for the future to enjoy.

"The best brains of the world today should be directed towards making it such a monument that the future will respect the past," Moir said.

Such a statement could still be a clarion call for the national city.

Luckily, Canberra is still a good place to see high quality architecture - if you look past the dross, both old and new. But on the trail of Malcolm Moir and Heather Sutherland, there's a feeling that right around the corner there will be another construction site or a hole in the ground where a worthy house once stood.

"It wasn't like today, where in fact things can be built up very quickly, knocked down, built up, knocked down. In those days, and certainly up to the last 20 years, people have been really careful about their places and looked after them," Freeman says.

"We're losing that - quickly."

Thoroughly Modern: The Life + Times of Moir + Sutherland Architects by Peter Freeman. Uro Publications, 320pp. $75. Available from: mail@peterfreeman.com.au