Cadillac unveiled a concept CTS Coupé at the Detroit Motor Show this year, and now a prototype of an estate version has been spotted on test.

It’s expected to be unveiled at next year’s Detroit show and will go on sale in the UK to try and tempt drivers from their BMW 5 Series, E-Classes and A6s.

The sharp, edgy design of previous CTS models remains and power is expected to come from a 311bhp petrol V6 as well as a 2.8-litre.

Crucially, GM has a 2.9-litre V6 diesel that will be critical for fleet sales in Britain.

It may get a 6.2-litre supercharged V8, developing 550bhp, to take on the BMW M5.