A cherished 19th- century picture at the heart of Newport's art collection has been snapped up by a London dealer after the city's council failed to top a £16,500 bid.

Ironically, it was Newport's pioneering research into the work of James Flewett Mullock that may have increased its value on the open market and put it beyond the city's reach.

"This is definitely one that slipped through our fingers," Roger Cucksey, the city's keeper of art, said.

"It is an extremely important painting and central to Newport's history, but there just wasn't the money there to top the winning bid.

"There is an arrangement in Wales by which the National Library of Wales continued bidding, but even they had to drop out at £13,000.

"The man who bought the painting is a dealer with an interest in this period. There is a great appetite for work of this kind, especially in America."

Sir Charles Morgan at the Castleton Ploughing Match, an oil painting completed in 1845, was important not only as a picture in its own right, but as a record of Gwent in the mid-19th century, Mr Cucksey said.

"In 1982, when we became very interested in Mullock as a local artist, we made contact with Dr Roderick Howell, in Swansea, the owner of the picture, who loaned it to us.

"You could tell the quality of the work the moment you saw it. It was quite stunning.

"When Dr Howell died I was authorised to make a bid, but we were never really in the running.

"Mullock is extremely important in Gwent history as a painter who recorded local events and scenes just before the widespread introduction of photography. Mullock's picture of the Chartist attack on the Westgate Hotel in 1839, for example, is almost certainly an on-the-spot record.

"The composition of the ploughing picture is excellent, giving us a fine depiction of the landscape and of Lord Tredegar, as well as being a record of the animals and ploughing techniques."

An exhibition of Mullock's work was put on at Newport's art gallery in the 1990s. A book by John Wilson issued at the same time, and which is still in print and for sale at the museum, has a foreword by Mr Cucksey.

He said: "We put Mullock on the map and now we are victims of our own success. In 160 years this is probably the first time the painting has been out of Wales.

"I would have loved to have acquired it, but that's the way the market goes."