The Antiques Roadshow has made its first seven-figure valuation, putting a £1m tag on a model made by the sculptor Antony Gormley of his gigantic Angel of the North.

This is more than Gateshead council paid for the full-height statue — and more than three times the previous record for the show, held by a collection of silver dating from the reign of Charles II and valued at £300,000 in 2006.

The show, in which experts value heirlooms and knick-knacks brought in by members of the public, draws about 9m viewers. Most items are worth only tiny amounts but, occasionally, a trinket that its owner had thought was valueless turns out to be worth thousands.

Tonight’s programme on BBC1, presented by Fiona Bruce, will feature the bronze model, known as a maquette. It was filmed at the Sage centre in Gateshead in September.

The maquette, 6ft high and 17ft across, was brought in by a local man who is an enthusiastic admirer of the sculpture. It is believed to be owned by the council in Gateshead, where Gormley’s statue stands beside the A1.

It had apparently been kept in council offices for 13 years and was transported in a crate inside a lorry by a team of council workers. They are clearly astonished when the value is announced by Philip Mould, the London art dealer.

Gormley, Britain’s best-known living sculptor, first discussed his plan for an angel with Gateshead council in the early 1990s. Although the Labour-controlled council was keen, there was opposition from Conservatives, Liberal Democrats and local residents.

They did not like the size of the statue beside a main road on the outskirts of the town. They also objected to the expected cost of just under £1m, even though half of it was paid by the lottery.

In response, the sculptor and the White Cube gallery in London made several models, some in cast iron and others in bronze. “Gateshead was short of money so we helped them by making quite a lot of maquettes to sell the idea,” said Gormley this weekend.

The steel angel, 66ft high and 178ft across, was finally unveiled in 1998.

Mould believes that his valuation of the maquette is conservative. A cast-iron angel maquette was sold at Sotheby’s in July for £2m. Most of the other models have been sold all over the world, according to Gormley. “Nonetheless, the story of its find and now its valuation is amazing,” he said. “I did not know this one was there with the council.”

Other notable “finds” on the show have included a Richard Dadd watercolour that turned up in 1986. It had been missing since 1857 and was bought by the British Museum for £50,000. A collection of Beatrix Potter illustrations was valued in 2003 at £250,000.

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