The owner's expression gave nothing away. With quiet dignity, he picked up his picture and bore it away through the crowds gathering for a mid-morning sale at Halls' auction rooms in Shrewsbury.
Mr Allen is the director of the fine art department. His views on pictures are much sought after since his recent spectacular success with an ink-and-chalk drawing by the 17th-century master, Carlo Maratta. For decades it had been pinned to the kitchen door of a Wolverhampton council house, partially hidden under a succession of tea-towels that helped preserve it from steam and grease.
Its progress to the Louvre, via Sotheby's in New York, is a saga worthy of John Mortimer's auction-house drama, Under the Hammer - except that it might be considered a little far-fetched. The famous Parisian museum already had two of Maratta's works. It was prepared to part with dollars 57,500 (pounds 38,590) to acquire a third.
The idea of luring the Louvre's bidders to Shrewsbury was not really on. Mr Allen has enough contacts to know exactly where to get the best price. He worked for Sotheby's for 25 years, joining them as a porter straight from school with little more in the way of qualifications than an A-level in art.
'One of the senior directors, Jim Kiddell, took me under his wing and taught me so much,' Mr Allen recalled. 'I longed to have half-moon specs and grey hair like Jim.'
By the time he accepted an amicable redundancy from Sotheby's a year ago, he had at least acquired a greyish beard.
Back in his native Shropshire, Mr Allen was soon established in an office that offered him a panoramic view over the River Severn.
Halls is a long-established firm, about 150 years old, with a tradition of selling livestock and the contents of farmhouses. But without expert advice, valuable items can all too easily be missed at clearance sales.
Mr Allen recently found a collection of 20 Wisden's cricketing almanacs that had been dumped in a bin. They went for pounds 2,000. And celluloid film from Disney's Cinderella, which had languished for years in a brown envelope, sold in New York last year for pounds 7,000.
The decision by Paul Willcock, the senior shareholder at Halls, to set up a fine art department is already paying handsome dividends. Turnover from antique sales has increased by 200 per cent, from pounds 500,000 to pounds 2m.
The Maratta was the department's second major find in less than six months. In September, it had unearthed two Chippendale chairs in clearing the estate of an elderly couple.
This time the detective work was done by Mr Allen's fellow expert, Robert Miller, another former Sotheby's employee who has found life in the provinces far from dull. His alarm bells rang when he turned the chairs upside down and noticed the characteristic Chippendale notches in the seat frames.
The resulting surge of adrenalin was enough to sustain him through hours of research. As two handsome 18th-century chairs they had been valued at pounds 3,000. As Chippendales, they were finally sold in Shrewsbury for pounds 60,000.
And on that occasion, Halls had all the commission, rather than a percentage.
Mr Miller has had no artistic training. He went to Sotheby's straight from university with a degree in philosophy.
'A lot of people there are willing to share their knowledge, and you just soak it up if you're the type,' he said.
He is still only 30, but comes across as someone with a wealth of experience. That experience, coupled with diligent research, makes the difference in a business where the rewards can put you in touch with great works of past genius, and where the possible pitfalls can leave a substantial deposit of egg upon one's face.
'I've also had more than my fair share of luck,' he admitted.
He has made the most of it for the past 10 years. Was it just luck that drew his attention to a Japanese vase amid a vast collection of cheap pottery in the tiny terraced house of a deceased sailor in Birkenhead? The vase sold for over a quarter of a million pounds.
Was it just luck that he walked into a farmhouse sitting-room in Ulster and came face to face with a marquetry cabinet and stand attributed to Pierre Gole, a Dutchman who worked for Louis XIV?
'We thought it might make about pounds 80,000, but it finally went to the Rijksmuseum in Amsterdam for pounds 300,000.'
Back in Wolverhampton, meanwhile, the former owner of the Maratta drawing has been in hospital undergoing heart surgery. He doesn't wish to be identified in case the imminent arrival of a large cheque from New York leads to the loss of his council house.
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