Plans by the United Kingdom's largest teaching hospital to expand its central London site have been threatened by a controversial rival bid. The Aga Khan has offered £24m ($35m; €39m) for the land adjacent to St Thomas's Hospital—twice the previously valued cost—to develop an Islamic cultural centre.

The billionaire spiritual leader of around 20 million Ismaili Muslims wants to build the biggest Islamic museum and cultural centre in the English speaking world. It would include a public museum, library, and academic facilities. Government ministers are keen to see him find a suitable location in the capital. He has previously failed to buy the site of the Royal Army Medical College and if he is unsuccessful again, he may decide to abandon the United Kingdom and look elsewhere.

The site, opposite the Houses of Parliament, is currently owned by King's College, London, who acquired the land in 1998 after a merger involving many of the NHS trusts in London. It is largely disused, although one building houses part of the medical school library. Guy's and St Thomas's NHS Trust had, however, been hoping to redevelop the land to house a school of nursing and a chemical incident unit but can only afford to pay £12m.

The college has been in negotiations with the Aga Khan for more than six months. The principal, Arthur Lucas, issued a statement supporting plans to increase academic presence on the St Thomas's site, “The college must retain a strong and active academic presence at St Thomas's Hospital and intends to remain deeply involved with the Trust in developing the partnership in academic medicine at that hospital, as well as with its other partner hospitals.”

The land has been part of St Thomas's for over a century and the proposals to sell it off have been heavily criticised by hospital staff. Speaking to the Times newspaper, which originally reported the Aga Khan's bid, Kevin Burnand, professor of vascular surgery, said, “It would be a disaster for us and the NHS if this land was lost. Many of my colleagues and I would chain ourselves to the railings in protest. The academic status of St Thomas's relies on expanding such a site for our library and other vital facilities that London needs.”