Classic car insurance specialists Hagerty has released a new report which details the most financially viable old timers to restore.

Of course, embarking on a classic car restoration can be seen as a one-way street to financial ruin, but are there cars out there that would offer a decent return, making the whole exercise worthwhile for more than just the love of it?

Hagerty breaks down the value of more than classics in its Price Guide using four criteria, ranging from Condition Four (fair: a driveable but imperfect classic) to Condition One (concours: one of the best in the country). It compared the value different between a 'fair' example and a 'concours' example to determine which classics offered the best financial return upon restoration.

Topping the list was the expected collection of exotica – the Ferrari 250 GTO, often cited as the world's most valuable car, topped the list with a £13.12 million difference between 'fair' and 'concours'. It was followed by the AC Cobra Daytona Coupe (£8.364 million) and the McLaren F1 (£5.74 million).

These are the UK's most financially viable classic cars to restore

Meanwhile, at the other end of the list was Ford Focus 1.6i Zetec – a recent addition to the list – with a £1,400 difference between 'fair' and 'concours' condition examples. It was followed by the Austin Allegro 1750 4-door saloon (£2,150) and the Vauxhall Magnum 1800 saloon (£2,200).

Obviously higher value cars like Ferraris and McLarens are going to top the list when prices are concerned, but looking at percentages – looking at the 'fair' value as a percentage of the 'concours' value, the Series 1 Land Rover Discovery was the clear winner, with a difference of £13,400 representing 91 percent of its 'concours' value. It beat the Lancia Beta 1600 S2 HPE estate, which had a £10,200 difference that equated to 89 percent of its top value; and the Lancia 2000 Berlina (£8,000 or 88 percent).

At the bottom of the list was the Ferrari 250 GT SWB (not to be confused with the aforementioned 250 GTO, with a six percent (£410,000) difference. It was followed by another Prancing Horse, the Ferrari 365 California Spider (£328,000 or 10 percent) and the Lamborghini 3500GT at 11% (£70,500 or 11 percent).

These are the UK's most financially viable classic cars to restore

Hagerty found the most financially viable restorations by looking at a combination of the two factors to see which cars presented a significant value difference.

Porsches topped that list with the 356 on top, specifically the pre-A cabriolet top (a £391,000 difference or 72 percent). The 356 'A' coupe was third on the list with a difference of £172,500 or 70 percent, with the two being separated by the Bentley S2 Continental drophead by Park Ward which had a value difference of £217,600 or 71 percent.

The least financially-viable restoration was the 

At the bottom, the TVR Cerbera came out last with a £13,700 (36 percent) difference, followed by the Porsche 924 Carrera GT (£27,800 or 36 percent) and the Maserati Ghibli (£59,800 or 30 percent).

These are the UK's most financially viable classic cars to restore

"The best reason to restore must be to return a car to a level of mechanical and aesthetic quality that delivers an enjoyable and safe driving experience to the owner," said John Mayhead, Hagerty’s head of valuation. "Above everything else, if the owner thinks it is worth it, then it probably is.

"Classics are built to be enjoyed and at Hagerty we want owners to drive their cars as often as possible. Buy a car you like first and foremost, and should it deliver a healthy return financially treat it as the icing on the cake."

Gallery: These are the UK's most financially viable classic cars to restore