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Marked for renowned London instrument maker Jesse Ramsden, c.1772, the 14½in radius Vernier sextant would have been a desirable object in itself, but another inscription proved crucial: G Vancouver.

On the day, three or four room bidders battled it out at Charles Miller's (24% buyer’s premium) sale - no phones or commission bids were booked, curiously, and it went to the London trade.

This instrument, which had been estimated at £10,000-15,000 in the sale held at the 25 Blythe Road auction hub, was not only marked for George Vancouver but was probably used by him on Captain Cook’s second (1772-75) and third (1776-79) voyages of discovery.

Not that the vendor had made the connection to the great Royal Navy surveyor whom the third largest city in Canada is named after.

He had bought it in 2005 from the estate of a retired RN officer in Devon among a job lot of various bits and pieces. It was only many years later that he noticed the inscriptions on a very dirty frame.

Miller said: “He realised it had a name on it but when he did find the name he didn’t even know who Vancouver was.”

Vancouver was just 14 when he set sail with Cook in 1772 and he was taught how to use instruments such as this sextant. He was certainly no shrinking violet, however. On his return three years later surviving correspondence shows he was writing to “London’s most senior instrument maker and whinging about things”, says Miller. He criticised the error of the arc and Ramsden took the sextant back to examine it personally.

“Ramsden would have been incandescent with some little whippersnapper telling him his instruments were not up to scratch,” adds Miller. “But Vancouver was apparently that kind of character and could wind people up.”