A 233-year-old clock - whose case was made by the Birmingham engineer Matthew Boulton - fetched nearly three times its asking price when it was sold yesterday for more than #400,000.

Before the sale experts believed the clock, made around 1772 during the reign of King George III, might fetch between #100,000 and #150,000, but the bidding swiftly overtook the conservative estimate to reach a final price of #411,200.

The clock - described as an important English ormolu musical and quarter chiming clock by Thomas Wright and Matthew Boulton - was found covered in dust in an attic in a country house near Salisbury, Wiltshire.

The catalogue description read: ?Despite the dirt of centuries and some losses, the high quality of the castings and the rich gilding of the case can still be admired.

?The mechanism is complete and awaits only a clean before it will once again musically announce the quarter hours and play a tune before striking the hour.?

Of the 409 lots in the Fine Clocks, Watches, Barometers, Mechanical Music and Scientific Instruments sale yesterday, the Boulton clock was the most valuable item sold at yesterday?s event.

?The fact that Boulton produced so few of these clocks, because at the time they were so unsuccessful, makes them incredibly rare,? said Mr Hills. ?There are only four known.?

Mr Hills said he could not reveal who had bought the clock. The first clock case Boulton produced, in conjunction with Thomas Wright, was in 1771 for King George III.