It was one option put forward by ministers when a dock strike in 1982 held up parts needed for the completion of the Thames barrier.
The situation compounded existing fears of a serious flood with “disastrous consequences” as the banks of the river had been raised in preparation for the barrier. It meant that any tidal surge before completion would be funnelled upstream.
The government however recognised the “major political difficulty” in “deliberately flooding Kent and Essex in order to protect central London”.
And in the event, the dock strike was resolved, the four gates which had been stranded in Teesside by the industrial action released and Thames barrier completed later that year.
The extraordinary situation was revealed in a file covering contingency plans for a major Thames flood released today by the National Archives.
A memo from the Department of the Environment stated there was a one in 50 chance of a flood between late August and late April and warned of “disastrous consequences” of what would probably be “the most damaging natural disaster liable to affect these islands”.
It detailed how there would be hundreds of casualties and deaths, polluted water, electricity failure, structural damage, disrupted telephone communications as well as a risk of looting and other outbreaks of civil disorder.
It goes on to state “substantial parts of the flood area would be virtually uninhabitable and mass evacuation may be needed”.
The memo also refers to the Armed Forces’s operation, code named giraffe, which included arrangements for military personnel and contractors to be on stand-by to repair breaches and for reconnaissance of flood areas and the carriage of VIPs.
The file reveals the government was concerned the continual delay to the construction of the Thames barrier caused by the dock strike could “give rise to a serious situation next January/February, when the risk of a tidal flood is at its highest”.
It was also concerned that Ken Livingstone, the then leader of the Greater London Council, would try to use the situation to “put the Government rather than the strikers on the spot”.
He had written to the prime minister, calling for the government to intervene in the dock dispute, the file shows.
“It has been suggested that a relaxation of current financial constraints might possibly be helpful in resolving the overall dispute,” he wrote.
“With male adult unemployment of the order of 20 per cent on Teesside, the reluctance of the dockers to accept any settlement which might lead to the loss of still more jobs, is understandable.”
A Cabinet Office memo referred to a paper by the Minister of Agriculture which considered a number of options, including trying to secure a resolution of the pay dispute between the Tees and Hartlepool Port Authority and the dockers, trying to persuade the dockers to release the gates and using the military to load the gates.
The memo also revealed the paper had suggested “if all else fails it might be necessary to provide that, if a major surge of water was threatened, that flood defences downstream would be breached so that some of the water would flood low-lying land in Essex and Kent rather than central London”.
It acknowledged however that “this approach seems unlikely to be practicable”.
“It would involve the destruction of large sections of defences which together have cost £20 million,” the memo stated.
“Explosive charges would have to be laid in advance so that they could be detonated when it seemed that a tidal surge sufficient to flood London seriously was on its way.”
Adding “There is a major political difficulty in that the Government would have to take responsibility for deliberately flooding Kent and Essex in order to protect central London”.