The reveal follows that of the estate-shaped Touring version, which made its debut at last month's Frankfurt motor show.
The four-wheel-drive B3 uses a re-engineered version of BMW's 3.0-litre six-cylinder petrol engine, with twin turbocharging and a performance cooling system to deliver 462bhp and 516lb ft of torque. The saloon version will accelerate from 0-62mph in 3.8 seconds, with Alpina claiming a top speed of 188mph. A slightly lower top speed of around 186mph for the Touring makes it one of the fastest compact estates on sale.
The previous B3 produced 404bhp in standard form and 433bhp in S spec, while the BMW M340i Touring delivers 369bhp. With the upcoming M3 climbing to more than 500bhp in top spec, that leaves a large power window for Alpina to be positioned in.
As has been the case with all previous Alpinas, the B3 gets a bespoke suspension tune aimed at bettering the ride comfort of the standard 3 Series, but with adaptive dampers allowing sharper body control at the flick of a switch. The ZF eight-speed automatic gearbox has been retuned for faster response and quicker shift times, while the xDrive four-wheel drive system and BMW's limited-slip differential have been tweaked to cope with the upgraded powertrain.
The B3 also receives a number of visual differences over the 3 Series Touring. As well as Alpina’s trademark multi-spoke wheels, available in 19in or forged 20in designs, it also features a more aggressive bodykit and quad exhausts. The interior has bespoke upholstery and badging, too.
Order books open in early 2020, with the first deliveries expected next summer. Expect a price of more than £60,000 for the standard B3 and more than £70,000 for the eventual B3 S.
Alpina has been modifying, developing and partially assembling its own takes on fast BMWs for decades and has a close relationship with the brand. Its recent models, such as the B5 and B7, have actually beaten BMW’s own M variants to market, which will also be the case with the new B3. It was initially expected that BMW's new M3 would be revealed first, but that now isn't the case.