One of four works painted on a grand scale in the late 1760s, the 3ft 9in x 6ft 7in (1.15 x 2m) oil on canvas was deemed amongst the most impressive vedute ever produced by Guardi and was the largest example to come to the market since another from the same series made a premium-inclusive £10m at Sotheby's in Monaco in 1989.
Estimated at £15m-25m, it was the subject of a lengthy phone battle as the bidding went up in increments of £500,000. The final price was the second highest for any Old Master.
Last week's auction series also saw a £20m record for George Stubbs, as well as a £5.8m record for Thomas Gainsborough, both at Christie's.
The buyer's premium at both salerooms is 25/20/12 per cent.