The four-wheel drive technology celebrates its 20th birthday next year, and is being introduced to the latest S-Class.

Mercedes says demand for four-wheel-drive cars still isn't strong enough for it to offer it in right-hand drive markets, but it hasn't entirely ruled it out.

'If demand increases, then we will offer it,' said Hands-Dieter Multhaupt, Mercedes vice president of product development.

The decision to launch 4Matic relies on interest from other right-hand drive markets such as Japan and Australia. Mercedes says it doesn't have the economies of scale to develop right-hand drive 4Matic for the UK alone, so the UK will have to wait for other markets to prove there's enough demand.

The permanent four-wheel drive system sends 45% of the engine's power and pull to the front wheels and 55% to the rear.