It was sunk over the Nab rocks east of the Isle of Wight to replace a lightship after the war, and is a well-known landmark for sailors as it lies off Spithead and marks the deep-water eastern entry into the Solent.

[4][5] During the First World War, the British Admiralty designed eight towers codenamed M-N that were to be built and positioned in the Straits of Dover to protect allied merchant shipping from German U-boats.

Designed by civilian Guy Maunsell, the towers were to be linked together with steel nets and armed with two 4-inch guns with the idea of closing the English Channel to enemy ships.

When these were flooded, the structure sank and settled to rest at an angle of 3 degrees from vertical towards the northeast – a characteristic tilt which is obvious to this day.

[11] The Nab Tower was manned as a lighthouse, but also functioned as a Royal Navy signal station;[6] and during World War II it was equipped with a pair of Bofors guns to provide some defence to the Solent approach, and actually shot down several aircraft.

In 2013, Trinity House commissioned BAM Nuttall to undertake a major refurbishment programme due to extensive corrosion of the upper levels, meaning it was unsafe to land helicopters upon the helipad.