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25 April 2016

Mystery Towers of Southwick

Judy Middleton 2002 (revised 2016) 

copyright © J.Middleton
This fine photograph of the Mystery Towers was one of a series captured by Mr Ridley of Southwick.

A Mystery

The local populace dubbed these two peculiar structures Mystery Towers because nobody had any idea about why they were being built. They were constructed during the closing stages of the Great War and even in 1920 their purpose was still an official secret although the war had been over for two years by then. Meanwhile people were fascinated by them and speculated about their use. It seems local photographers were not shoed away from this secret work and many postcards were produced, capturing them from every possible angle.


copyright © J.Middleton
A closer view of one of one of the towers
 reflected in the water.
In those days there was a tidal waterway that ran from Shoreham Harbour to the west end of the Power Station and was parallel to the canal on the south side; it went by the unromantic name of The Gut. It seems that during the Great War the Admiralty took over The Gut and that is where the peculiar monsters were built.

A single-track railway was laid to the site in order that materials for construction could be easily transported. This track left the main line on the embankment near Southwick Railway Station. When the end of the short line was reached, a novel operation got under way – in some ways reminiscent to a toy railway track. The rear part of the track was lifted up and taken to the front and then laid down and so the train proceeded at a snail’s pace.

The line also had the disadvantage of having to go over the lock gates, which was fine when there was no movement of vessels. But when a collier or other ship needed to sail further into the canal, cranes had to lift the track away.

Sir Alexander Gibb (1872-1952) was the man responsible for the design of the towers and he was the Navy’s Civil Engineer-in-Chief. Scottish-born Gibb came from a line of engineers and he was articled to famous engineers John-Wolfe Barry and Henry Marc Brunel. Gibb had wide experience because he had been involved with railways as well as being appointed in 1916 as Chief Engineer of Ports Construction to the British Army in France; the post also came with the rank of Brigadier General. In 1919 he went to work for the new Ministry of Transport and was its first Director General. In 1921 he left Government service because he decided to set up his own business as a consulting engineer. He founded Alexander Gibb & Partners in 1922, which became the foremost British engineering firm whose expertise was utilised world-wide.

Captain D.J. Morgan RN was put in charge of the group of Royal Engineers who worked on the Mystery Towers. While the work was in progress these man camped out at Southwick Green.

U-Boat Menace

 copyright © D.Sharp
A German U-boat washed ashore at Hasings, 40 miles from Shoreham Harbour.

The purpose of the Mystery Towers was to act as a sophisticated defence against the menace of the dreaded German U-boats. The idea was that from eight to twelve steel and concrete towers would be sunk in a 55-metre depth of water across the English Channel via the Varne Shoal and there would be chains and steel nets slung between them. The towers would guard the strategic stretch of water from Folkestone to Cap Gris Nez.

The official title of the scheme was the Admiralty M-N Scheme or Project M-N.

The weight of each tower was around 10,000 tons; the base measured some 60 metres across and was 25 metres in height and this concrete raft was constructed of interlocking cells. Above the base rose a column composed of 1,000 tons of steel measuring 27.5 metres in height with a width of 12 metres. 

A gangway led to the top of the tiers and the base of the tower-shaped structure was divided into a number of floors. On the second lowest floor there was an electrical plant for lighting and heating purposes. The men’s quarters were located on the next floor and the officers’ berths on the floor above; there were still two more decks more. These decks were to provide enough accommodation for 60 to 100 men.

At the top of the structure there was a crow’s nest or conning tower with the control room underneath.

By adjusting the sluices of the structure, which had a flat bottom, the tower could be submerged or raised.

The towers were to be armed with two standard 4-inch guns and searchlights. But the towers were also to accommodate the latest technology including a hydrophone and a galvanometer to detect the presence of submarines. 

The scheme was an incredibly expensive project and it is said to have cost £12 million, which was a considerable sum in those days.

The project did not start until 1917 and it was not until November 1918 that two towers were at last completed; this was despite the work being on-going both day and night. Work was still in progress on two further towers when the war ended.


On 23 May 1920 members of Southwick Urban District Council were invited to visit the Mystery Towers. Captain Clift had invited them but he would not or could not enlighten them as to the purpose of the structures. However, the councillors did gather that one theory being bandied about was untrue; this was that the towers would be used to raise sunken ships.

The view from the top deck was astonishing ‘the country is laid in a charming bird’s eye view like a lovely piece of tapestry’. Even the nearby lighthouse resembled a small toy.

But it was not just officials who could enjoy the view, ordinary members of the public were allowed to visit as well and the fee charged was sixpence or one shilling. One young lady who took advantage of the offer was Marie Masters (née Mitchell) and she had every right to be interested because her father was one of the civilian workers at the site. Marie’s family lived at 15 St Nicholas Road, Portslade. They rowed across the canal and Marie sturdily climbed her way up to the top despite being seven months pregnant. However, when she arrived at the top and saw how high up they were, she lost her nerve. She was quite unable to get back down all the stairs under her own steam and had to be carried down.

copyright © D.Sharp
Mr Mitchell was a civilian worker on the Mystery Towers. The family lived at St Nicholas Road, Portslade.

Another civilian from Portslade who worked on the Mystery Towers was Albert Bowles (1900-1978) from Shelldale Road. He was born just over the Downs in Poynings. Albert joined the Royal Sussex Regiment at the age of 16 but was discharged when it was discovered he was underage for military service. What his work involved at Southwick was also a mystery to his family too because he would never speak about it; people in those days were very conscientious about keeping silent where confidential matters were concerned. Albert moved to Shoreham during the Second World War and he died there in 1978.

 copyright © D.Sharp
Another civilian worker was Albert Bowles (inset) who lived in Shelldale Road, Portslade.

Nab Lighthouse

On 12 September 1920 one of the towers was towed away. The operation took place on a Sunday and it had to coincide with the highest tide of the year otherwise the task would have been impossible. Marie’s father, Mr Mitchell, went with the tower and he always maintained that it was such a tight squeeze there was only a leeway of around 18 inches on either side.

Eight tugs were employed in the tremendous task of shifting the tower and they continued towing it for a distance of 53 kilometres until the Nab Rock was reached off Bembridge, Isle of Wight. The tower was to replace the Nab Rock Lightship and it became the basis of the Nab Lighthouse; Mr Mitchell was on hand to help fill the base with concrete.

Second Tower

In 1922 the second tower was demolished where it stood and Mr Mackley was one of the men engaged on this work. After completion he founded the firm of J.T. Mackley, supervising engineers and contractors based at Small Dole.

The reinforced concrete partitions, which formed the cellular construction, were cut into convenient slabs measuring some 3 feet by 2 feet and sold off for paving; many of them were utilised in local garden paths and terraces, while some formed the foundations of glasshouses at Worthing.

When the old Power Station was being demolished in 1990/1991 workmen digging out the foundations came across the concrete base of one of the towers.


It is important to remember that the Mystery Towers were in fact at the cutting-edge of new technology in their day. It has been claimed that they paved the way for the construction of modern sea oil-rig platforms.

It is also worth noting that Guy Mansell was among the Royal Engineers working at the site. During the Second World War he designed the Mansell Sea Forts.


Argus (26 November 1997)
Encyclopaedia of Hove and Portslade
Internet searches
Middleton, Judy Portslade and Hove Memories (2004)
Sussex Life (August 1983 / November 1983

Copyright © J.Middleton 2016
page layout by D.Sharp