Classic car and motorcycle buffs will tell you that the history of a classic vehicle is even more important than what it is - and the more paperwork there is (it's called provenance in anorakspeak) the better, especially if the bike has a successful racing history.
And it's a matter of record that the most valuable motorcycles in the world are pre-war British V-twins; a Brough Superior SS100 was recently auctioned at a record £250 000 (R3.5 million).
So the classic motorcycle world is buzzing with the news that the most important Brough Superior of them all is up for sale - and it could wind up as the world's most expensive second-hand bike.
The bike in question is 'Old Bill', built in 1922 by Brough Superior for the personal use of company founder George Brough. It had a 1000cc side-valve, V-twin engine and, when it made its racing debut at Brooklands, it gave the Brough his first win and became the first side-valve motorcycle to lap the historic Surrey track at an average speed of more than 100mph (160km/h).
CRASH AND BURN
But this was 90 years ago and the tyres of the time weren't really up to it; later that day the new bike put its rider in hospital after a front-wheel blowout.
When he got back on his feet Brough convinced his family that hill-climbs and sprint racing (what we now call drag racing) would be safer than circuit racing, and rebuilt the bike - now named 'Old Bill after a First World War cartoon character - with special forks and a one-off racing engine built for him by James Arthur Preston of JAP fame.
With Brough in the saddle, it went on to win 51 sprints in the 1922/1923 seasons. And in the 52nd, at Clipstone in Nottinghamshire, it recorded the fastest time of the day, even though bike and rider crossed the line separately!
With Brough once more in hospital, the factory staff converted his 'works racer' to road trim and sold it out from under him to pay the wage bill.
Since then its history has been easy to follow.
While it was in storage during the Second World War in its owner's house (note we said house, not garage) it was badly damaged when a cast-iron bath fell through a ceiling, and it remained off the road until the late 1950s, when it was bought by 'Titch' Allen, founder of the now 16 000-member Vintage Motorcycle Club and renowned Brough enthusiast.
With the help of George Brough himself and former works manager Ike Webb, the bike was restored to its 1923 specification. Its first public appearance was a demonstration run at Clipstone in 1959 with George Brough aboard - and under strict instructions to stay that way!
CLASSIC TT
Allen also did demo runs at the Brighton Speed Trials and at Brooklands before passing the bike in 1988 to his son Roger, who was then chairman of the Vintage Motorcycle Club's racing section and an accomplished historic racer.
Roger Allen fitted 'Old Bill' with a sidecar so he could run it in sprints with his wife Sue as passenger, and he also ran it in solo trim in the 1991 Isle of Man Classic TT races - the first time a Brough had competed on the island.
Sadly, Allen was killed racing a Triumph in the 1992 Classic TT, after which Sue put his motorcycle collection, including 'Old Bill', on display at the Nottingham Industrial Museum, where it has been ever since.
Now, however, George Brough's personal sprint bike is to be auctioned, and is expected to fetch £250 000-£270 000 (between R3.1 million and R3.4 million) - but it’s not inconceivable that it could set a new record for a classic motorcycle auction.