ON a recent day trip to London my route took me from Kings Cross via Bloomsbury to Soho and beyond.

With half an hour to spare, I walked and thought, in particular about how the city has changed.

I first visited in 1970, drawn in part by an image that had been put into my head by reading about Dylan Thomas, who was a denizen of Soho in the post-war era when many of the houses had been bombed to the point where they looked like ruined castles.

Then, pubs were where people of artistic bent mingled. But for every Thomas there were many more who talked a good poem but never seemed to get round to writing one. Soho in the 1940s, observed the Irish writer, Anthony Cronin, "was largely inhabited by failures".

It was also the one area of the metropolis where a true bohemia flourished. "The sort of artist who emerged from it," he added, "was apt to be a higher type than the success-oriented younger poets or painters of the fifties, but he was also apt to be a more than usually highly developed misfit.'

Uppermost in Cronin's mind were the two Roberts, Colquhoun and MacBryde, a major exhibition of whose work opens this weekend at the Scottish National Gallery of Modern Art.

This, one hopes, will bring belated acclaim for two painters who have long been overshadowed by contemporaries such as Lucien Freud and Francis Bacon. Even north of the Border, from where both Roberts hailed, mention of them rarely meets with a flicker of recognition. While this is regrettable, it is no more than one has come to expect. Where cultural history is concerned we have much catching up to do.

I first encountered Colquhoun and MacBryde in the pages of a memoir by Julian Maclaren-Ross, who is lightly disguised as X Trapnel, an eccentric and egotistical writer, in Anthony Powell's A Dance to the Music of Time.

Maclaren-Ross first encountered the Ayrshire pair during the war. True to form, MacBryde went immediately on the offensive, querying the authenticity of Maclaren-Ross's Scottish accent and accusing him of being a phoney.

The two Roberts had alighted in London a couple of years earlier, having met - and fallen in love - at Glasgow School of Art. Both came from working-class backgrounds and both were fiercely Scottish. Initially at least, they were avowed Nationalists and wore kilts as a matter of course. Even more distinctively, they made no attempt to dilute their accents and talked in an argot Burns would have recognised. MacBryde in particular could be scarily argumentative.

Once MacLaren-Ross asked him what he thought about when sober. "Do you prepare apologies for the people you've been rude to the night before?"

MacBryde paused for a moment, then replied: "Maybe I'm thinking up a new lot of rude things to say next time I'm drunk."

Such is the stuff of myth in which the stories of Colquhoun and MacBryde abound. At a time when homosexuality was illegal neither of them made any attempt to be what he was not. Concealment was not in their character.

When they had success, which they both enjoyed into the 1950s, they spent extravagantly. But that was fleeting. By the end of the decade of the angry young men, their paintings, which are evocative of Braque (in MacBryde's case) and Picasso (in Colquhoun's), stopped selling. When they were away on a trip their flat was trashed and much work was vandalised.

Now effectively homeless, they had no option but to call in favours from friends who let them sleep on a floor or in a bath. With no studio, it became impossible to paint and their income dried up. Drink took its inevitable toll. Colquhoun died, aged 47, in 1962, in MacBryde's arms. MacBryde, survived for four years without his beloved other, then, recalls Eddie Linden, who knew him well, he was hit by a car while doing a Highland Fling in the middle of the road, and died. He was just 43.

Their relationship, remarked Cronin, was like alcoholism. Both Roberts needed booze as much as they needed each other. They have often been described as the last of the bohemians, which distinction they perhaps deserve. What one can say without fear of contradiction, however, is that their Soho is no more.