The 15 x 5in (38 x 12cm) panels of two Dominican saints by Fra Angelico which will be offered for sale at Dukes next March.

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When offered for sale at Dorset auctioneers Hy Duke next year, they may well become the highest selling picture lot ever offered outside London.

Guy Schwinge of Dukes has estimated them in excess of £1m, but admitted it is difficult to predict the price that such historically important works will make.

Paintings by Fra Angelico are hardly common on the market. The last comparable pair of panels by the artist to be offered in this country were at Sotheby's in 1972 when they made £230,000, a figure which equates to just under £2m in modern prices.

Attributed to the Renaissance master by Dillian Gordon, the curator of early Italian paintings at the National Gallery, they are the two 'lost' panels from a series of eight that once surrounded Fra Angelico's main altarpiece of the Church of San Marco in Florence. Commissioned by Cosimo de Medici himself, four of the other six are now in the Lindenau Museum in Germany, one is at the Museum of Fine Art in Minneapolis and one is at the Art Institute of Chicago.

ATG understands that there have already been enquiries from more than one serious international buyer following on from the publicity that was generated in the national press last week.

"We were very fortunate to get the chance to conduct the valuation at the house," said Mr Schwinge, adding that there were also a good number of pre-Raphaelite works in the collection, including a Burne-Jones and a Rosetti.

The consignment comes from the estate of Jean Preston, a former librarian whose father had acquired them in the US in the 1960s. Under export regulations, it would be unusual for a work to be refused an export licence if it has been in the UK for under 50 years. This may therefore further help the panels in setting a provincial high for a pair of paintings.

The current record stands at £900,000 for two portraits by Jean Baptiste Greuze (1725-1805) sold at Dreweatt Neate at Donnington Priory in February 2006.

By Alex Capon