The original map of Winnie-the-Pooh’s Hundred Acre Wood by the artist EH Shepard has set a world record for a book illustration sold at auction, selling for £430,000.

The 1926 sketch, which was privately owned and had been unseen for nearly half a century, introduced readers to the world of Christopher Robin and his friends in the original book.

Purportedly drawn by Christopher Robin himself, the map is littered with spelling errors – “nice for picnicks” and “100 aker wood” – and is captioned “Drawn by Me and Mr Shepard helpd”.

The London auction house Sotheby’s had estimated its value at between £100,000 and £150,000.

“We’re extremely pleased, obviously,” said Philip Errington, Sotheby’s senior specialist in the book department, who said there had been significant international bidding.

“It reflects the fact that people fall in love with the works of AA Milne and EH Shepard. The map is part of the defining world of Winnie-the-Pooh. However you approach Pooh, whether it was through a book or a Disney cartoon, the map is your way in. It is the first thing you encounter. It has a resonance.”

Shepard illustrations are not rare at auction, according to Errington, with the first sold by Shepard himself in the 1920s. “They are out there and do well on the market. But the important thing is that this hasn’t been on the market for 50 years. There was particular desirability because it hasn’t been seen for so long,” he said.

The previous record for a book illustration was also held by Shepard: Poohsticks Bridge, an ink drawing of Christopher Robin and his bear playing their favourite game, which featured in AA Milne’s book The House at Pooh Corner, was sold by Sotheby’s for £314,500 in 2014. The 1928 drawing had also been held in a private collection, for 40 years.

Before that, a 1890s watercolour illustration by Beatrix Potter, the creator of Peter Rabbit, held the record after selling in 2008 for £289,250.

This was the third time Shepard’s original map had been sold by Sotheby’s, after it fetched £650 in 1968 and then £1,700 in 1970. “So we look forward to seeing it again in another 50 years,” Errington said.

Four other original Winnie-the-Pooh illustrations were also sold at the auction on Tuesday. The five drawings sold for a combined total of £917,500, including buyer’s premium. Experts had estimated the five would sell for £310,000-£440,000.