Most of us on our wedding days can look forward to some blissful certainties about our future lives together but on their November 1915 wedding day (in Sydney) George and Kate knew that they were soon to be parted. They knew that George was soon to sail away to the war. And so of course they must have at least fleetingly entertained, on what should have been a day of wall-to-wall bliss, the terrible thought that George might never come back. Emotions we can't imagine must have lurked in their young minds.

This wedding photograph is, literally, the poster picture for the National Library of Australia's Keepsakes: Australians and the Great War exhibition that that opens on Wednesday. And as well as being on the exhibition's posters the picture, massively enlarged, is fixed to the library's noble, Parthenonesque facade.

And in this case this photograph is given special poignancy by the library's discovery of an important living rello of the poster couple. What's more Barbara Searle, 87, daughter-in-law of the just-married couple, knew them well and remembers them clearly. She was in Canberra on Tuesday and talked to us about the portrait. Some of the hard-to-define power the Great War has to touch us and unsettle us is that it and its stresses and horrors were so very recent. George and Kate are not creatures of the Olden Times but are still up and out and about in the memories of the living.

We sequestered Mrs Searle, a softly-spoken, white-haired vision in a swish white outfit at the exhibition and in front of the now-famous photograph. Later, over morning tea with lamingtons and Vegemite sandwiches she got a tiny coffee stain on one leg of her hitherto flawless ensemble and was not amused.

"I married their [George and Kate's] eldest son, Colin. Colin had been overseas [for World War II] in the air force. I was 19 when I got married and Colin was 29. They [gesturing at the couple in the photograph] were about 24, 25 on the day they married.

"After Colin came home from the war and while we were waiting to work out what we would do we lived with them [the in-laws, and at Coonamble]. Because housing was incredibly short after everyone came home from the war. So living with the in-laws was nothing unusual."

As Mrs Searle began to discuss the personalities of George and Kate we found ourselves peering into their wedding-day faces to see if we could see there traces of what she, Mrs Searle, was reporting about them.

"He was a delightful fellow. He liked lots of company. But she [more reserved] was a product of her very strict Presbyterian upbringing. And she was one of 13 children. She became a wonderful grandmother to my children."

We agreed that the wedding photograph is a very touching artefact.

"I think it was taken in November 1915. He had joined up in September. So they married in November and he went overseas in December. Probably the decision to marry was brought on by his enlistment, the certainty of his serving overseas. I think a lot of the men wanted to get married before they left. But it is poignant. Especially to think of the number of widows caused, all the women that were never able to marry because of the war's high death rate."

But George, one of four brothers to sail away (one of them was killed at Ypres in 1917) was only gone for about six months because he contracted some exotic stomach bug and was shipped home with a gastric ulcer. He did try to enlist again, in 1918, but was knocked back on health grounds. He went on to have a distinguished career in local government in western NSW.

She thinks, from memory, that he almost never talked about the war. Mrs Searle noticed the same reticence in her late husband Colin.

"He was a navigator on Lancaster bombers and he didn't talk much about it at all except to admit that he was scared the whole time."

The discovery of Mrs Searle and her presence in Canberra (she still lives in the bush in the west) is the result of some prodigious detective work by Susannah Helman, one of the curators of Keepsakes. It was only about 10 days ago one of Mrs Searle's sons received the crucial, inquiring phone call from the library.

We wondered what feelings were being kindled in Mrs Searle by being beside the photograph and at the exhibition for which it is the poster.

"I know this will sound corny," she confided, and went on to say (not sounding corny at all) that she liked to think that, yes, if there really is a Heaven to which we all go that an amazed George and Kate might be sitting on a cloud and looking down at the huge wedding picture of themselves draped on the library building and marvelling "What on earth's going on?"

What's going on, until 19 July 2015, is the National Library of Australia's Keepsakes: Australians and the Great War exhibition. Admission is free.