Porsche will reveal the all-new 911 at next month's Frankfurt Motor Show - but images of the new sportscar have already been leaked in the US, showing Porsche's icon uncovered for the first time.

They reveal an evolutionary design (well, you wouldn't expect anything else, would you?) but with proportions and detailing better-honed than ever before.

Porsche has codenamed the new 911 '991' and has given it more powerful flat-six boxer engines: the base 3.4-litre produces 350hp, the regular 3.8-litre producing 400hp. Both are greener too. Cleverly, the body uses a mix of aluminium in its construction, a bit like the Audi TT. This reduces weight and ensure the new 911 is even faster.