Sealand has been hit by a blaze (Picture: Harwich Lifeboat)
The blaze on Friday has badly damaged Sealand, an inhabited former military platform, about eight miles east off the coast of Essex and Suffolk.
A coastguard spokesman said it was believed a generator caught fire. The one person on board was airlifted to Ipswich Hospital.
The so-called "independent state" of Sealand is home to an internet firm.
A helicopter from Wattisham airfield rescued the injured man from the platform and Harwich lifeboat were also called to the scene.
'Territorial waters'
Britain built the anti-aircraft platform during World War II.
It remained derelict until the 1960s when a retired Army major, Paddy Roy Bates, took over the 10,000 sq ft platform and declared it the independent nation of Sealand.
At the time, the platform was beyond the then three-mile limit of British territorial waters. All this changed in 1987, when the UK extended its territorial waters from three to 12 miles.
The British Government does not recognise the sovereignty of Sealand.
Fire being extinguished by tug boat

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The Principality of Sealand is currently being checked, after a fire caused havoc to the ex-World War II tower. Fire fighters from the Thames Coastguard poured water onto the structure, and rescued a security guard who was taken to Ipswich hospital by an RAF helicopter, suffering from smoke inhalation. It is believed that the fire was started by a fault in a generator. The Harwich off-shore lifeboat team attended the platform, and described the top platform as having caught alight due to an 'electrical fire'.

Sealand, formerly HM Fort Roughs, is a self declared principality comprising of an old army fort. It was built to deter, and report back on, any German attempts to lay mines using aircraft in the channel of the Thames. The offshore company HavenCo used it to hold servers for the computer industry.