For more than 30 years, between 1962 and 1996, a nuclear reactor sat at the heart of London tantalizingly close to a busy thoroughfare and to people’s homes and public buildings. Its existence so close to the metropolis was kept a secret from the public, because to tell the truth would have been extremely controversial.

The reactor was located at the basement of King William Building at the old Royal Naval College in Greenwich. The Royal Naval College was established in 1873 and was housed in a 17th century building complex designed by the highly acclaimed English architect of the time, Sir Christopher Wren. The buildings originally housed the Greenwich Hospital—a retirement home for disabled sailors of the Royal Navy. The word “hospital” merely meant a place providing hospitality. After the hospital closed in 1869, these buildings became the Royal Naval College where navy officers were trained.

The Old Royal Naval College in Greenwich, the site of the world’s only reactor ever installed inside a Grade I-listed 17th-century building. Photo credit: Mark Ramsay/Flickr