The new stretch of the M74 over Beattock summit bypasses many a previous road there, beginning with the one the Romans built. It also obliterates a forgotten but historic motorsport course where, in the late 1930s, the MG Car Club ran the first ''modern'' car sprint meeting in Scotland.

Car enthusiasts here were way behind their motor-cycle equivalents in organising speed events, as opposed to rallies and trials, after speed competitions were banned from public roads in the twenties. Motor-cycle racers like Jimmy Guthrie could compete at the long established Scottish Speed Championships on the West Sands at St Andrews, and there were other sand races at places like Balmedie, Lossiemouth and Powfoot.

Dirt-track racing, later to be called speedway, was introduced first of all at Celtic Park, and then at the Marine Gardens in Portobello, although Celtic Park was replaced as the Glasgow venue by the White City track near Ibrox.

Speedway meetings attracted crowds of more than 20,000, who came to cheer on the likes of Billy Galloway, Drew McQueen and Norrie Isbister, who is still to the fore today.

Between the wars, Scotland had no circuit motor racing as we know it nowadays, but the first private-road speed hill climb was organised in 1934 at Bo'ness by the Scottish Sporting Car Club. Bo'ness was well established by the time the MG Car Club found its new venue near Beattock summit.

The word sprint wasn't used in those days, and the title of the event was the Howcleugh Speed Trials. The course was on a loop of the old Glasgow to Carlisle road by that time in private ownership. Track features included a rather dodgy bridge, where chicanes were put in place to slow the cars down.

John Flint, in the first customer model Frazer Nash-BMW 328, won the opening event in 1937 from George Simpson's Ford V8, Simpson being the intrepid character who had previously persuaded an Austin Seven to the summit of Ben Nevis.

However, Flint's winning time of 35.1 seconds was beaten by AJ Cormack in a demonstration run with his Brooklands Alta single-seater. Cormack's 33.6 seconds meant an average speed of about 54mph which, considering the chicanes, was pretty fast going.

Next year, the pace was set by two drivers sharing the same car. Leslie Thorne in the Ford V8-engined Alexander Special trimmed the course record to 32.9 seconds, with George Simpson 0.7 of a second slower. Both felt they could go faster, and talked the organisers into letting them have an unofficial extra run.

Thorne could not beat his previous winning time, and Simpson, who had already managed a ''phenomenal avoidance'' during practice, when he met a non-competing car in the braking area, had an accident he recalled in precise detail for me 45 years later.

Going like the clappers, he clipped the bridge, was flung right across the road through the boundary fence and, having parted company with the car, made a personal crash landing in the paddock by the finish line. Somebody went with a stiff drink to Mrs Simpson, who hadn't seen the incident, and warned her there might be some very bad news about her husband. But George was fine.

He remained fine for many years after that. When the Forth Road Bridge was nearly ready, he approached the authorities with a proposal to hold a race over it during the run-up to the formal opening. His idea was an Avus-style layout, the two carriageways serving as straights running in opposite directions. Officialdom, as you might expect, chased him.

After the 1938 event, the MG Car Club abandoned Howcleugh, where the surface and the ''Simpson'' bridge were deteriorating. The 1939 speed trials were moved to an ash circuit on the network of roads at the Achilles School of Motoring, on a now built-up site behind the Bilston Inn on the A701 between Edinburgh and Penicuik. JP Millar's Frazer Nash-BMW took 1m 51.3s for the best two-lap run, just a tenth ahead of Mirrlees Chassels's chain-drive Frazer Nash.

The owners of the motoring school had plans to attract more events, and even to bank the corners, so allowing higher speeds. But this was July 1939, and Hitler made sure there would be no 1940 season.