Merlin Entertainments has announced plans to build the biggest, most intense ride ever at Alton Towers theme park, UK.

The £18m (US$28.9m) roller coaster – codenamed Secret Weapon 7 (SW7) – is expected to open in March 2013.

SW7 will have a capacity of 65 passengers with a top speed of 52mph and a 30m drop.

The coaster, which will open on the site of the old Black Hole attraction, will have a track length of 1,170m and a ride time of 165 seconds.

The theme park's bosses said the 'world-first element' of the ride is still under wraps, but claimed it would be different from traditional roller coasters.

Thrill-seekers can experience a taste of what is to come by braving The Sanctuary, a new attraction at the resort, which has opened as part of this year's Scarefest and is a prequel to the new rollercoaster.

Katherine Duckworth, head of consumer marketing at Alton Towers, said: "Details of the new ride coming to the theme park in 2013 are still a closely-guarded secret but we know that people are hugely excited about its arrival and want a hint of what is to come."

The new ride will add to Alton Towers' existing line up of white-knuckle rides including Air, Oblivion and Rita.