Leaked: Images of new BMW Z4 design surface

Images of the third-generation BMW Z4 have surfaced online after the German car-maker was caught patenting its Porsche Boxster rival's design ahead of its launch at the Paris motor show in October this year.

The design renderings, unearthed by autoweek.nl, appeared online late last night and are believed to be genuine. They show how BMW plans to evolve the stunning Concept Z4 that was unveiled in August 2017 at the Pebble Beach Concours in California.

These new images of what's thought to be the 2019 Z4 production car show a long bonnet, short rear proportions and simple fabric roof, but suggest BMW has significantly toned down the surface design from its last year's concept.

Biggest change involves a considerable redesign of the front-end that sees the Concept Z4 lose its gaping-wide side air intakes and dramatic aero-blade.

The twin kidney grilles have also been slimmed down and the headlights redesigned for mass-production.

It's a similar story towards the rear of the car, where the bumper is now less sculptured while the show car's carbon-fibre diffuser has been dropped.

Developed under the 'G29' codename, to save costs the forthcoming Z4 will share its architecture with the next Toyota Supra.

Under the bonnet, expect both a longitudinally-mounted turbocharged four- and six-cylinder petrol engine, with the flagship Z4 M40i to offer almost 300kW.

BMW hasn't announced whether or not an Z4M is in the pipeline, but the M40i is almost certain to come with suspension, brakes and an electronically-lockable rear differential honed by the German car-maker's performance division.

Already seen testing, we do know the third Z4 will ditch the old car's folding metal hardtop for a lighter fabric roof.

With a body that's considerable stiffer than the last model's, the latest BMW Z4 could finally give the benchmark Porsche 718 Boxster a run for its money.