Beloved BMW tuning house Alpina is celebrating its 50th anniversary in consummate style. Two special edition models, limited to 50 units a pop (naturally), will be rolled out and they will be the fastest cars the firm has ever built. Dubbed "Edition 50," there will be 50 sedans or estates and 50 coupes based on the B5 Bi-Turbo and B6 Bi-Turbo, each with a heavily revised 4.4-liter V8 powerplant.

With engine components revised for "very high performance with long life," Alpina-specific turbos with custom water-cooled intercoolers, new lightweight pistons and shorter air intake, the Edition 50 boasts output of 591 hp and 590 lb-ft of torque. With a 0-62 mph time of 4.2 seconds and top speed of 204 mph, Alpina claims this is the quickest, most powerful, car it's ever made. To reduce weight, Alpina made changes to its 20-inch wheels, which are now 15.6 kg lighter, while a titanium exhaust from Akrapovic saves a further 17 kg. Some aerodynamic upgrades were also made to the special hand-crafted body in BMW's wind tunnel.

Inside, unique features include a plaque engraved with the signature of Alpina founder Burkard Bovensiepen, hand-crafted black leather sports seats, piano black trim with Edition 50 etched into the panels, and '1965-2015' logos on the seat backs, carpets and key ring. Available in Alpina Green, Alpina Blue, or a bespoke Edition 50 Sepia created by BMW Individual, prices will start from £86,850 in the UK.