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The Mersey Estuary Sea Forts

Although never used for offshore radio broadcasting there were three Army Sea Forts located in the Mersey Estuary as part of the World War 2 defences for Liverpool.

Following the success of his pioneering Navy Sea Forts in the Thames Estuary, the Admiralty commissioned Guy Maunsell to built sea forts for the Army to use to defend the Mersey Estuary.

The forts were intended to defend vital seaways from enemy aircraft, intercepting them before they reached the docks and industrial heartland of Liverpool. Because the perceived threat was so high, a new modular design that could be built and placed more quickly was chosen.  

The Mersey Estuary has many sandbanks and Maunsell decided that its shifting sea bed would be too soft to support the kind of flooded-pontoon founded forts he had built for the Navy in the Thames Estuary so an alternative design was devised.

The Army forts were founded on a self-burying grid of concrete which was integral to the rest of the structure - the idea was to not impede the natural movements of sand and shingle.

Also each Army fort was not a single structure, but seven individual towers linked by walkways and they were set out in a formation known to be successful for land-based fortifications. Each tower consisted of four slim reinforced concrete legs founded on one of the self-burying grids. The legs supported a two storey octagonal steel accommodation pod with military equipment on the roof.

Although the Mersey forts were constructed first, and were in deeper water, their basic design was followed for those built later in the Thames Estuary.

Originally 38 towers were intended for the Mersey Estuary, but only 21 were built (three forts). (Plans for 13 towers in the Humber Estuary were abandoned. A further 49 towers were planned for the Thames Estuary but only 21 were built - three complete forts).

The Mersey Forts were built, from October 1941 onwards, at Bromborough Docks on the Wirral side of the River Mersey by Cleveland Bridge & Engineering Co Ltd,  each tower taking about eight weeks to construct.

The completed forts were deployed in the Mersey Estuary between 7th October 1942 and 25th July 1943.  

The Mersey Estuary sea forts were never engaged in enemy action.

Demolition of the Mersey Forts began early in the 1950s - their disposal was given a higher priority than those in the Thames Estuary because they were regarded as a hazard to ships navigating towards the River Mersey and Liverpool Docks.

However, demolition was delayed in 1954 when the salvage ship working at Queens Fort was diverted to assist with the urgent demolition of The Nore Fort in the Thames Estuary, which had been damaged following a collision with a Swedish ship and the remains were considered hazardous to shipping in that area.

Demolition of the three Mersey Forts was finally completed in 1955

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One of the Mersey Estuary Forts

Photo: Weekend Echo


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