The water system at No Man's Land, based in the Solent outside Portsmouth naval base, is now off limits "until the health risk is controlled".

The measure was introduced after Isle of Wight Council health officials took samples from the Victorian fort.

The move came after a Midlands man who visited the fort contracted the bug.

'Potential to be infectious'

A Council spokesman said: "Preliminary results of water samples taken have confirmed the presence of legionella bacterium at levels with the potential to be infectious.

"The proprietors are continuing to work closely and in full co-operation with the relevant authorities.

"The council understands that the individual who contracted legionnaires disease, prompting this investigation, has made a satisfactory recovery.

"No other cases have been linked to these premises. "

The armour-plated fort boasts a variety of facilities for corporate and private hospitality including weddings.

Designed in the 1860s to prevent French ironclad warships bombarding the strategic dockland at Portsmouth, it was de-activated after World War II.