THOMAS Telford was arguably the greatest civil engineer Britain has ever produced and as a new book reveals it is the magnificent Pontcysyllte Aqueduct near Wrexham that is probably his masterpiece.

In World Heritage Canal - Thomas Telford and the Pontcysyllte Aqueduct, author Paul A. Lynn, discusses Telford's humble beginnings before describing his self-propelled rise from journeyman stonemason to famous canal engineer.

"I've been interested in canals for about 25 years and to go over the aqueduct in a narrow boat with my wife was one of the most exciting things we've ever done on the canal," laughs Paul, a professional engineer from Bristol.

"There have been a number of books about Thomas Telford in recent years but they have either tended to be quite scholarly works or they are tourist books which deal with the nice time people can have on the canal.

"I wanted to aim my book at a slightly wider audience and it is heavily illustrated with over 100 pictures so I hope it looks attractive but at the same time it is not trivial and contains a lot of engineering detail and putting Telford's work into its historical and social context, showing him as a remarkable mix of good-natured ambition, talent and resilience."

Completed in 1805, Pontycysyllte Aqueduct carries the Llangollen Canal across the River Dee in the Vale of Llangollen in north east Wales. The 18-arched stone and cast iron structure is for use by narrowboats and was completed in 1805 having taken ten years to design and build. It is the longest aqueduct in Great Britain and the highest canal aqueduct in the world.

"I think the most remarkable thing about it is was that Telford used an iron trough on top of the stonework to hold the water," says Paul. "It had never been done before and was an extremely bold thing to do as most people thought he was crazy.

"He had to align 126 foot high stone pillars out of the river Dee and put an iron trough on the top - many engineers thought what he was doing was impossible and that the trough could never hold the water high above the valley. It was a remarkable design and is what really marks it out as special."

The aqueduct was to have been a key part of the central section of the proposed Ellesmere Canal, an industrial waterway that would have created a commercial link between the River Severn at Shrewsbury and the Port of Liverpool on the River Mersey.

But by the mid-1800s, railway ownership continued to grow and many canal companies sold out because they were no longer profitable. In many cases the new owners deliberately let the canal decay in order to reduce the competition with their railway.

"The decline was in way the fault of Telford," continues Paul. "There was a 'canal mania' during the 1790s which saw a frenzy of canal building quickly followed by a financial slump because Britain was in the Napoleonic Wars. There was no way Telford could have predicted the Ellesmere Canal would never be built as intended.

"The irony is that the aqueduct now has many more boats crossing it than it ever did when it was a commercial canal but it just goes to show how well designed it was that it is still in use more than 200 years later."

In the latter half of the 20th century, leisure boating traffic began to rise and a rebranding exercise by British Waterways in the 1980s, saw the former industrial waterway renamed the Llangollen Canal. It has since become one of the most popular canals for holidaymakers in Britain and is now maintained and managed by the Canal & River Trust. The richly-deserved UNESCO award has put the aqueduct and its canal back in the limelight.

"It has really brought the aqueduct more attention and much more than when it only interested canal enthusiasts," adds Paul. "It made such an impression on my wife and I when we spent a week on the canal there as did Telford himself.

"In many ways he was such an unassuming man in contrast to Isambard Kingdom Brunel who was a great self publicist. He was much more modest and that really endears him to me."

World Heritage Canal - Thomas Telford and the Pontcysyllte Aqueduct by Paul A. Lynn is available in all good book shops and from publishers www.whittlespublishing.com