The portrait of Mary Wordsworth has only once been on public display

The painting - a portrait of Mary Wordsworth, Lady Kent - was sold on Thursday in London at Sotheby's Important British Art auction.

The final sale price was the second-highest paid to date for a Reynolds' work at auction after his portrait of Omai was bought for �10.3m in 2001.

Sotheby's head of British pictures, David Moore-Gwyn, said the amount paid for the Mary Wordsworth portrait indicated the renewed interest in Reynolds' work.

"We are delighted with these exceptional results which prove beyond all doubt that, since the sale of Omai in 2001, Reynolds' work can command prices of an entirely new order," Mr Moore-Gwyn said.

London exhibition

The portrait of Omai was sold to Tate Britain earlier this year after a mystery donor gave the gallery �12.5m to save the work for the nation.

The portrait of Mary Wordsworth had been in the same family since 1949.

It has been on public display only once, when exhibited at London's Royal Academy in 1893.

The work was painted in 1777, a time when Reynolds is considered to have been at his peak.

Reynolds was the leading 18th-Century portrait painter and the first president of the Royal Academy, London.