The new project is more modest than a £120m plan which would have put the whole South Bank arts complex under an undulating glass roof designed by architect Richard Rogers, which was rejected by the Arts Council of England.

Now a National Lottery grant of £12.5m has been earmarked for the first stage of restoration and refurbishment of public spaces at the hall, which is a Grade I listed building.

A glass lift will be part of improved public access to the venue, and a balcony will be opened up overlooking the River Thames.

An acoustic study is also being carried out on the Royal Festival Hall's auditorium, which was criticised by conductor Sir Simon Rattle as "the worst major concert arena in Europe".

Diverse range of events

More than 2.5 million people visit the Royal Festival Hall each year. Best known for classical concerts, it has recently diversified into hosting a wide range of musical events, including rock, jazz and world music.

It is part of the South Bank complex, which is also home to the Queen Elizabeth Hall, the Hayward Gallery, the National Film Theatre, the Royal National Theatre and the Museum of the Moving Image.

Sir Simon Rattle called the Festival Hall the worst venue in Europe

But the complex web of performance halls, galleries and elevated walkways have been called eyesores since they were built in the 1950s and 1960s.

Chief executive Karsten Witt said he hoped the restoration would restore some of the original feel to the building, built as part of the 1951 Festival of Britain.

He added: "We will enable many more people to make the most of our unique riverside setting by restoring the roof terraces, with their spectacular panoramic views of the London skyline.

"We will make the building more exciting by reinstating the original main entrances, clearing access routes and improving orientation."

Culture Secretary Chris Smith called the grant "excellent news".

Other plans proposed

He said: "It is another step forwards in the revitalising of the South Bank site, with the emphasis in this case on the Royal Festival Hall, one of the capital's most important post-war buildings and a world-renowned centre of excellence for the performing arts.

"This will be a fitting way to celebrate the Hall's 50th anniversary."

Other plans to improve the rest of the South Bank proposed last year include the demolition of the Hayward Gallery, the Queen Elizabeth Hall and the Purcell Room

The buildings would be replaced with new low-rise buildings that provide more open space.