TIRELESS volunteers who have spent nine years restoring the largest known Bull engine in the world are ready to let off some steam.

The group, based at Kew Bridge Steam Museum, are finally set to unveil the fully refurbished 150-year-old water-pumping device next month following the mammoth project.

They began toiling on the decommissioned three-storey high steam engine back in January 1999, and have spent thousands of hours returning it to working condition.

The hard-working bunch, who have removed rust, scraped, painted, polished and dismantled, while shovelling tons of mud and silt from the damp and dark basement, are delighted it is all over.

"We're all extremely happy it's ending - it has taken far longer than we ever imagined," said volunteer Richard Albanese, 37, from Strand-on-the-Green.

The engine is named after the engineer Edward Bull, who helped devise the steam cylinder and piston pump contraption with Harvey & Co in Cornwall in 1856.

It was originally based at Kew to deliver clean drinking water to reservoirs near Notting Hill Gate and ran until 1944, when it was taken out of service along with other engines at the site.

"The Bull engine is the largest of its type in existence and the only example remaining in its original location," said Nick Morgan, secretary of the Bull Engine Restoration Committee.

"It is also, now, the only working Bull in the world. The engine will now be demonstrated regularly and visitors will be able to witness the awe-inspiring sight of this massive engine working just as it did during its long working life of over 80 years."

The project was funded thanks to a £14,500 donation by the Heritage Lottery Fund and a further £20,000 grant from the Museums, Libraries and Archives Council.

The re-commissioned engine will be launched by Brentfordbased broadcaster Anna Ford in a special ceremony at Kew Bridge Steam Museum on May 12.

It will then open to the public for the first time the following weekend, with demonstrations on Saturday and Sunday, 17 and 18, May between 2.15pm and 2.45pm.

For more information contact the museum on 020 8568 4757.