Lambeth Council's planning committee last night approved ambitious plans for the redevelopment of the South Bank's Royal Festival Hall.
The planning permission for the Grade 1 listed building was granted at a special meeting of the committee held at St John's church in Waterloo.
The building's foyers will be renovated, the original entrance restored and new public spaces opened up, including a new cafe on the Belvedere Road street level.
"This is an important first step in the redevelopment of the whole of the South Bank site to create a world-class cultural centre."
The refurbishment is likely to cost £54m and costs will be met by the National Lottery through the Arts Council of England and Heritage Lottery Fund.
A public fundraising campaign, launched to mark the RFH's 50th birthday last year, has already raised more than £4 million.
The plans for the Festival Hall include a new extension building alongside the adjacent Hungerford Bridge, an education centre and a new glass lift linking all levels.
The auditorium's acoustics and technical facilities will be modernised and the seating made more comfortable.
The full timetable for the improvements will be finalised over the summer and work will then be put out to tender.
The planned modernisation has been supported by London Mayor Ken Livingstone and represents the first stage of a masterplan for the whole 27-acre South Bank site, being put together under the direction of Rick Mather.