''When you look at how the money [for cancer research] is spent most of it is allocated to common cancers that affect people later in their lives,'' Mrs Wallace said. ''Only a fraction is spent on these rare and aggressive cancers that kill children and young adults.''

This Christmas and new year will deliver a double dose of grief for Lachlan's family. The young car enthusiast, public servant and husband died just 11 days short of his 26th birthday.

When Summernats kicks off on January 2 it will be the first time since 2008 Lachlan hasn't entered his highly modified Datsun 1200 ute.

Mr Smith, who spent a decade doing the car up with Lachlan and is now its custodian, is in two minds about whether he should take it along. At this stage he doesn't think it is likely. He and Mrs Wallace, who remain close after separating when Lachlan was 12, are still coming to terms with their loss. So too is Chelsea, Lachlan's widow, and Oscar, the pug who was an inseparable part of Lachlan's life until the very end.

Now 15, and in less than perfect health himself, Oscar is a source of comfort for Mrs Wallace and other members of the family.

''They [dogs] know everything,'' she said. ''He has picked up on a lot of the sadness. Even though he doesn't move very well he follows us everywhere. If he can't be with you he will sit on your shoes. I've told him he has to hang on a bit longer yet; he can't go anywhere - Oscar is my support dog right now.''

Oscar, in deference to his age, stayed with Mrs Wallace and her partner, Paul, when Lachlan moved out to set up a new home with Chelsea in 2012. The couple married in March this year.

While Mrs Wallace and Mr Smith do not begrudge research into cancers that affect older people, they firmly believe more should be done to spare other families the suffering they have endured. ''While it is true that these cancers are very rare they do occur,'' Mr Smith said. ''And when they do they rob people of decades, not just years, of life.''

Mrs Wallace said the saddest part had been Lachlan's awareness of what was being taken away from him. He had never used the disease, which came into his life in January 2006 shortly after he graduated from Radford College, as a crutch or an excuse and went on to study at university, fall in love, travel overseas, marry, begin a career and develop a passion for motorsport.

''There are times when I feel I can really empathise with mothers who have lost their sons after they have gone off to war,'' Mrs Wallace said. ''Lachlan was fighting an insidious enemy; we never knew what it would do next or when it would strike or return.''

The interest in Summernats, which did not come as a total surprise given his father is a car tragic who still uses the LJ Torana he bought 40 years ago as daily transport, has resulted in the odd unexpected irony. One has been his 92-year-old grandmother's spirited defence of the event to her critical friends who talked it down every time it rolled around. ''Lachlan loved everything about it,'' Mrs Wallace said. ''He was definitely the other side of the event. Like a lot of people who took their cars he had invested a lot of time and money, was really proud of his car and was a very responsible motorist.''

That's not to say he didn't have a wild side; it was reserved for the racetrack however. One of Mr Smith's favourite memories is of travelling to Eastern Creek with Lachlan back in June. The cancer had returned and Lachlan was not feeling well but, despite this, he managed to log a 12.7-second 400 metre time in the turbocharged 1.8 litre ute with an exit speed of 172km/h.

It is this willingness to make the most of every moment that Mr Smith still misses and mourns. ''It is so hard to let go,'' he said. ''He always put on a brave face. I want people to know Lachlan was a wonderful person; he was gentle and caring and his mum relied on him very much.''

During his short, but passionately lived, life, Lachlan forged a special affinity with the specialists and nurses at the Peter MacCallum Cancer Centre in Melbourne. Readers wishing to support the centre can do so by visiting their website www.petermac.org