The Prince of Wales today unveiled the foundation stone for a new tower during a visit to Westminster Abbey.
The tower will be the first significant addition to the gothic church for more than 270 years and will house a lift and staircase which will take visitors to new galleries, 70ft (21m) above the Abbey floor.
The first official image of the tower - a watercolour - shows how the structure, which will open in 2018, will be almost hidden on the outside of the existing church, tucked away where a 1950s lavatory block used to be.
The tower will lead to the Queen's Diamond Jubilee Galleries, which are being built in the triforium - an internal gallery high in the church which has been hidden from the public for more than 700 years.
The Prince also visited craftsmen in the triforium, where treasures and collections reflecting the Abbey's 1,000-year history, will go on display in the new galleries. Exhibits will include royal funeral effigies, silverware, stonework and a crimson velvet cope worn by the Dean of Westminster at Charles II's coronation.
The Prince said during the visit: "I think it is a brilliantly imaginative project to find a way of utilising that really remarkable area that nobody ever sees. It is also an excuse to display some of the remarkable artefacts, all of these things that otherwise are so difficult for people to see."
The Dean of Westminster, the Very Reverend Dr John Hall, said: "This is a most exciting development which will allow visitors to the Abbey to see so much more of our wonderful treasures and to grasp the richness of the history of this holy place which represents faith at the heart of the nation."