Surprising as it may seem today, Jaguar had difficulty selling all the D-Types it orginally built, and when by the winter of 1956-57 and the anticipated target of 100 cars produced was in sight, the decision was taken to convert the 25 unsold D-Types into a new model, the XKSS roadster.

Announced in January 1957, the XKSS was a D-Type shorn of its rear fin with a specially-made windscreen, a full-width cockpit, extra interior trim, folding soft top and side curtains, nearside door, chrome bumpers and a luggage grid on the tail.

But production was dramatically brought to a halt when fire gutted the part of Jaguar's Browns Lane factory where the conversion was taking place, destroying nine cars and the associated tooling.

In the end only 16 XKSS roadsters were produced, most of which went to the United States.

Most famous of these was the "Green Rat" owned by legendary film star "King of Cool" Steve McQueen, bought secondhand in 1958 from a TV personality.

Today, the value of these ...