They are so sturdy and thick that for decades they stopped millions of gallons of water from pouring down the Caen Hill lock system in Wiltshire.

But now that the two-tonne lock gates are being gradually replaced on the Kennet and Avon canal, that quality is soon to be put to another purpose – at this year's Glastonbury Festival.

The 10-inch thick oak gates are ideal for sound-proofing, so festival creator Michael Eavis is using 70 of them to create a new venue at the June event – a Portuguese bullring.

Tipped on their ends and arranged in a circle, the 12ft high gates will create a 200-seat arena which will host drama, music, theatre and song, as well as mock bullfights with a real-life matador.

The venue, called Campo Pequeno, is the new addition to the Pilton event this summer, and the Glastonbury crew already has 50 of the gates from the canal work, with another 20 needed over the next month or so.

British Waterways has spent £1 million replacing the lock gates on the 29-tier complex just west of Devizes.

The gates were gradually replaced over the past few months, with much of the work happening in January when boat traffic is at its lowest, as part of a major refit which coincides with the canal's 200th anniversary last autumn.

Each time a gate is taken away, it ends up being stored at British Waterways yard in the town, before being transported to Worthy Farm.

Last year's lock gates ended up as bridges and walkways at the festival, but now a new use is being found for them.

"With soundproofing from these lock gates from Devizes, it's going to be fantastic," said Mr Eavis.

"It's going to have bullring seating with the lock gates going around and we're going to cut about eight or so medieval doors into it so it will have the same layout as a bullring.

"I've got this bullfighter coming over from Portugal with a cape to fight an artificial bull in a mock bullfight," he explained.

Gill Owen, from British Waterways, said because lock gates generally last between 15 and 20 years and the canal was restored in the 1980s, lots of the gates have needed replacing in the past year or two.

The organisation has a policy of reducing, reusing or recycling everything – even two-tonne lock gates – so the Glastonbury Festival project is ideal, she added.