For sale, one careful owner (and 720,000 miles on the clock)

Vincent Black Prince motorcycle to be auctioned after 56 years on the road

Love affairs come and go, but few can have endured with such lingering and obvious affection as that between Stuart Jenkinson and his motorbike Vinnylonglegs.

After more than half a century of happy times together, during which the retired chemistry lecturer has never forsaken the object of his desire for the allure of a younger model, the time has come to finally say goodbye.

In April, Vinnylonglegs – the name he gave to his beloved 1955 Vincent Black Prince – is to be sold at the Imperial Motorcycle Show in Staffordshire with an estimated price tag of £45,000.

The parting of the ways between the 83-year-old, who is now too weak to lift the bike, and one of the jewels from the heyday of the late lamented British motorcycle industry, will prove a sad occasion for the one careful owner of what is thought to be among the most travelled machines in the history of two-wheeled transport.

"It's a love affair of sorts. Yes, absolutely that's right," he said this week as he gave it the once over for one last time at his home in the Cleveland hills. "Selling it feels like selling a child. I feel so sentimental about it. A few women would have a feeling like that for a machine but there are plenty of guys like me who have fallen in love with a bike," he added.

Not that there have not been bumps along the way – a road which measures more than one million kilometres travelled together (721,703 miles) or seven times round the vehicle's well-used mileometer.

There was an early wobble over handling problems, three big ends worn out and replaced – and the time in Austria eight years ago when it nearly all ended in disaster on a winding Alpine pass.

Vinnylonglegs was Mr Jenkinson's third Vincent. Bought in Newcastle-upon-Tyne in the year Anthony Eden became Prime Minister, it cost £385.

"It was more than a year's wages in those days," he recalls.

It was one of the last motorcycles to leave the famous Vincent factory in Stevenage where Phil Vincent had been producing the prized machines which set many world speed records.

The Black Prince was billed by its creator as a "two-wheeled Bentley". Although not initially popular, its 1000cc V twin engine capable of a top speed of 120mph – achieved only once by Mr Jenkinson in 1957, travelling downhill with the wind behind him – was to prove adequate to his needs.

"I didn't have a car then and I thought a motorbike was poor man's transport and I would ride it for a while until I got a car," he recalled. Although he did graduate to the solidity of four wheels, it was never more than a device for moving from A to B.

"The Vincent is a magical bike – there is no other like it. I couldn't ride anything else," he said. In the early days there were no helmets or expensive leathers, so riders made do with a pair of strong brogues, heavy tweeds and a pair of ex-RAF pilot's goggles. He accepts he has been lucky, after having more than 100 crashes – mainly prangs in the icy Northumberland winter.

The worst occurred in Austria in 2002, when Mr Jenkinson was running a motorcycle touring company offering guided trips which took him to more than 40 countries. A fainting fit saw him come off and break his femur, collar bone and five ribs.

Seven years earlier, his wife Anne had finished accompanying him on his jaunts after coming to grief on a country lane in a thunderstorm in Yugoslavia. "She said: 'That is the last time I am ever going on that bike' – and it was," he said.