The Breitling Mulliner Tourbillon clock is an option for Bentley’s Bentayga SUV.

No one is immune to a bargain — not even those who can spend £30,000 on a watch. At Watches of Switzerland, an authorised dealer, an Audemars Piguet Royal Oak automatic in rose gold sells for £42,600, but the same watch is on offer at website Chrono24 — on the "grey market" of unauthorised sales — from US dealer Watch My Diamonds for $34,850 (£27,227). Impossible to ignore, the grey market is becoming a powerful force in the watch industry.

Unauthorised watch dealers such as Jomashop.com, Authenticwatches.com and IconicWatches.co.uk discreetly buy stock that authorised dealers have failed to sell, and offer them at a lower price, often with an equivalent warranty. Chrono24, an online marketplace similar to eBay where dealers and consumers can meet, is another heavyweight in the sector, with more than 10m monthly visits. Discounts of 30-40 per cent on new TAG Heuer, Breitling and Rolex watches, delivered overnight and offering responsive customer service, appeal to price-conscious shoppers.