"Peep, peep," Thomas said at the weekend when asked about the flotation. "Hurry up, hurry up, hurry up." The comment is characteristic of Thomas, a fussy, impatient, cheeky little engine who has always had a desire to make a big run in the wider world beyond his home station.
Since his first appearance in print in 1946, Thomas the Tank Engine has been the favourite character in The Rev W Awdry's books, The Railway Series. A Hollywood feature film currently in development should cement his position alongside such 20th-century icons as Mickey Mouse, Bugs Bunny and Fred Flintstone.
Mrs Allcroft, the company's founder, says she recognised Thomas's star potential when they first met in 1979, while she was doing research for a documentary film on railway preservation societies. The introduction was made by The Rev Awdry. "Thomas had leadership capability," she recalls. "He's very good at cheering the other engines up when they've displeased the Fat Controller and morale gets low."
Brian Sibley, author of The Thomas the Tank Engine Man, a biography of Awdry, suggests another reason. "Perhaps the secret of Thomas's success is that, of all the railway engine characters, his personality is closest to that of a child." Prince Charles adored Thomas when he was a boy, and so did his sons.
Such easy identification with the character, combined with high production values and a canny marketing campaign, have made Thomas a commercial success. In 1994, children demanded so many licensed Thomas products that the company was estimated to be worth pounds 50m. This year's flotation will probably value it at pounds 25m, with pounds 5m of new cash being raised. The company made a pre- tax profit of pounds 2m on turnover of pounds 11.5m in the year to June.
So it's not just the Fat Controller who's getting rich on the back of Thomas. The books, followed by the television programmes, have been a huge success. With sales of pounds 50m, Wilbert Awdry is the biggest children's writer of the century. Mrs Allcroft's 104 10-minute television episodes of Thomas the Tank Engine are now seen in 50 countries. More than 800 spin-off goods ranging from models to mugs and sweets to sheets are available.
Thomas was not the first of The Rev Awdry's engines, however. That honour goes to Edward, closely followed by Gordon and Henry. The Three Railway Engines was originally told to his son Christopher while he was ill with measles in 1943. Awdry's wife's insisted the three stories, and later a fourth bringing them all together, should be sent off to publisher Edmund Ward, whose company is now part of Reed Children's Books. Later he began making models of the trains in his stories, with sawn-off broom handles for boilers. He also added a fourth model, which became Thomas.
Thomas's early works were, however, plagued with problems, particularly with regard to the illustrations. The Rev Awdry is a railway buff, and was determined that both the stories and the pictures should be as accurate as possible. His plots were derived from real events on British and overseas railways. But while Thomas and his colleagues faithfully followed his direction, the illustrators were not always so diligent. In some cases extra wheels were added to locomotives, or buffers and windows changed so that, in the worst example, Henry ended up looking like Gordon.
The original series, published between 1945 and 1972, consisted of 26 titles, although Christopher Awdry, the lad with measles, has since added another 14. Critical acclaim followed popular adulation. Mary Cadogan, an authority on children's literature, said: "His engaging cast of headstrong or shy, boastful or understanding engine 'characters' have flourished and become archetypal." Brian Doyle, another expert, puts it down to the size of the books. "They can be slipped into small pockets without any trouble at all, to be taken out at convenient moments."
Thomas's first ventures into other media were not very successful. An early attempt to bring the series to television in 1953 ended in disaster. The programme was broadcast live, and the technicians proved they couldn't run a model railway. The illusion was completely undone when one of the trains derailed, and a god-like hand intruded into the shot to set it back on the track.
Radio and records, particularly a reading by John Gielgud in the early 1980s, were more favourably received, but an option on the television rights sold to Andrew Lloyd Webber, the West End musical producer, led nowhere. It was Mrs Allcroft's purchase of Thomas's television and marketing rights in 1979 that shot him to stardom. Until her programmes first aired 12 years ago, Thomas and his colleagues had sold 750,000 copies. During the first year of television the series sold 2 million, according to Mrs Allcroft.
Thomas the Tank Engine and Friends was shot at Shepperton Studios with a new technique that Mrs Allcroft calls "live action animation" and which her partner, Angus Wright, describes as "playing with trains and filming it". Thomas's fortunes have continued to roll along nicely ever since Shining Time Station, a series of longer television programmes incorporating the animated films, was produced for the US. And Thomas's biggest market is now Japan.
At first, persuading companies to invest in Thomas was as difficult as getting Gordon up the hill. At the Harrogate Toy Fair Mrs Allcroft was called mad. She recalls being told: "Today's generation haven't ridden on a train, let alone seen a steam engine."
There have been other operational hiccups, and even complaints that Thomas's railway has become a Very Bad Railway. One group of critics consisted of railway preservation societies which had begun running Friends of Thomas days to raise funds and public awareness of their activities. Many of these groups had strong ties to The Rev Awdry, and were alarmed when Mrs Allcroft raised the licence fee for use of Thomas from a nominal pounds 1 to pounds 100 plus 5 to 10 per cent of the gate.
When the third series of programmes came out The Rev Awdry was upset to discover that the etiquette of railway operation had been abandoned. New stories showed engines stopping in forests because they had made good time, something no engine would do in the real world. On one memorable occasion, in Mrs Allcroft's presence, he said: "That such rubbish should be credited to me is a gross insult." The producer, however, insists that "being famous has not changed Thomas at all".
Even more worrying in the long run could be the threat of political correctness. The stories have been attacked as sexist, with male engines in control, and female coaches following passively behind. Mrs Allcroft dismisses the distinction, noting that girls are just as keen on Thomas, and that in France he is known as Thomasine.
Although Thomas remains the face of the company, there are no plans to produce more TV programmes. The possibility of a Hollywood film aside, his main new works in future years seem likely to come from The Rev Awdry's son Christopher, should he decide that he still wants to maintain such a high profile.