THEY were hailed as Scotland's answer to the Mini, but quickly turned into a national laughing stock – famed for breaking down and seizing up.

But this week, champions of the Hillman Imp – manufactured during the 1960s and 1970s at the Rootes Group car plant in Linwood, Renfrewshire – will celebrate the 50th anniversary of a car that some believe was ahead of its time.

About 20 former workers will join Renfrewshire's provost Anne Hall on Thursday as she unveils a commemorative plaque at the St James Business Centre in Paisley – formerly the offices of the Linwood car plant – to mark the factory's opening by the Duke of Edinburgh on May 2, 1963.

Meanwhile, a convoy of 50 classic cars manufactured at the plant, including the Hillman Imp, will set off from Paisley to Coventry – once the headquarters of the Rootes Group. Organisers have appealed to any owners of a Hillman Hunter to get in touch to help complete the rally.

The event will be a chance for enthusiasts to honour a forgotten icon of Scottish motoring, scrapped in 1976 and followed in 1981 by the shutdown of the Linwood plant, which at its peak employed 9000 workers.

The Hillman Imp was born out of a post-war car boom. The Conservative government of the day introduced a scheme banning new car plants in areas which already had them. At the same time, grants were offered to companies willing to set up shop or relocate to deprived areas.

Linwood – with its high unemployment, proximity to Glasgow, motorways, air and rail links – seemed the ideal site. The plant would go on to manufacture 440,000 Imps. Unfortunately, the move proved disastrous for Rootes. The commercial failure of the Imp, first produced in 1963, ushered in a gradual takeover of the company by America's Chrysler corporation.

Paul Coulter, a Glasgow-based writer and author of a new book, Our Hillman Imp, said: "A number of things went wrong. It was a car that was way ahead of its time, and launched far too soon. The issues that led to the Imp's bad reputation were ironed out very early on in production – by 1964, 1965, all the major issues had gone. But that was too late - it was sealed with a bad reputation from day one.

"The irony was, the Imp was tested rigorously. They took it all round the world, to extreme climates from the North Pole to Africa, and all the tests were very positive. But they failed to test it in the manner in which it would be used. The Imp wasn't going to be bought by people who would be driving to the North Pole or Africa; it was bought by ladies living in East Kilbride who would drive to the shop, get their messages and go home again."

The hi-tech functions – an automatic choke, kingpins on the front wheels, and the pneumatic throttle – were prone to failure if the car went unused, leaving owners infuriated when it refused to start or move.

The aluminium engine was also vulnerable unless regularly topped up with water and oil, but many of its features – such as independent suspension and a rear opening hatch – were revolutionary in their day and now routine.

The Imp still boasts a loyal fan base. Scott Fanning, 39, a mechanic from Clydebank has been driving Imps since 1995. He has had his current model for 12 years. He said: "They were a cheap and cheerful runaround, good fun and reliable.

"I got into them when I was training as a mechanic and a guy at work used to buy them and do them up. I helped him with it and thought they were great."

There are now signs of a revival. Mr Coulter, who bought his first Imp when he was 17 and now owns five, said: "Three to four years ago you could buy an Imp needing restored for £200 and a really nice one for £1500. Now it starts at £1100 for an absolute basket case and to buy a nicely restored Imp you need a budget of up to £5000.

"Their popularity is going through the roof."