Campo di San Giacomo di Rialto in Venice by Canaletto – £1.7m at Sotheby’s.

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It was the cover lot of Sotheby's drawings sale on July 4 where it drew six bidders against a £300,00-500,000 estimate before selling to a European private buyer at £1.7m.

Campo di San Giacomo di Rialto was a rare 10 x 141/2in (25 x 37cm) drawing of a real Venetian scene - not an idealised view - and depicted the historic centre of the city's banking industry. Two paintings and a further drawing of the same view are also known, all held in public collections.

Produced with brown ink and chalk over a grey wash, it demonstrated the artist's masterly technique, acute observation and subtle handling of light. It had come to auction after Sotheby's received an unsolicited phone call from a vendor who was unaware of its value and whose family had owned it for around 100 years.

The price easily outstripped the previous record for a drawing by the artist which had been held for over 25 years - the $715,000 (£493,103) seen for view of Warwick Castle sold in New York in November 1986.