Iconic is an overused word, but it is perhaps excusable in the case of Marshall guitar amplifiers, with their handwritten logo, leather-look finish and raucous sound unchanged in 50 years. Something not everyone knows, however, is that, despite the all-American aura, Marshall is a British family company that grew out of a music shop in west London, and still manufactures old-school valve amplifiers in Bletchley.

So far, so retro. But Marshall knows how the modern world rocks. For the past few years, it has developed a line in well-received Marshall-styled accessories, from headphones to wireless speakers, designed by a collaborator, Zound Industries of Stockholm, and made in China.

Last month, however, Marshall did something less rock and roll than seemingly bonkers. It announced a Marshall mobile phone. The “London” is an Android smartphone that looks like a Marshall amp and is heavy on music features. On hand to give the lavish launch a rock and roll vibe were Glen Matlock of the Sex Pistols, Phil Campbell of Mot?rhead and Mick Jones of The Clash, plus a gospel choir singing the latter’s “London Calling”.