This month will see a day devoted to the subject of the venerable Ton-class minesweeper at the Royal Naval Museum in Portsmouth.

The seminar, on March 15, will study the involvement of these coastal minesweepers in home waters and overseas between 1953 and 1994.

The class first earned its spurs during the Suez Crisis of 1956, and also staged patrols in the Mediterranean during the Cyprus Emergency and in the Far East during the Indonesian Confrontation.

They covered tasks as far away as the Hong Kong Squadron, and as close to home as fishery protection work in the Channel and the North Sea.

The first ships of the class appeared from 1951, and most of them were built of teak wood on aluminium frames with an aluminium superstructure. Copper sheathing on the double-skinned hull was later replaced by a type of nylon.

The last Ton-class built – a variation on the wooden theme – was HMS Wilton, which was launched in 1972 and was the first major glass-reinforced plastic (GRP) warship in the world. She paid off in 1994.

The design of the class was led by shipyard John I. Thornycroft, and drew on lessons learnt in the Korean War; the ships were built using extensive quantities of non-magnetic materials.

Ton-class ships included versions which were minesweepers, with various types of towed equipment, including wire sweeps to sever the mooring cables of buoyant mines, and acoustic/magnetic influence sweeps which acted like large ships, triggering harmless detonations.

Minehunters used high-definition sonar to detect mines, which divers then classified and disposed of.

Weapons varied from ship to ship, with a single 40mm Bofors gun being a common fitting on the fo’c’sle.

The ships displaced between 425 and 440 tons fully loaded, with a speed of 15 knots. The original Mirrlees engines were replaced in later ships by lighter Napier-Deltics, producing 3,000hp on each of two shafts, the first ship to receive these being HMS Highburton.

In the Royal Navy, 116 Ton Class minesweepers were delivered between 1953 and 1960. Subsequently, 15 of these vessels were converted to minehunters with the addition of sonar to detect mines on the seabed, while others of the class were sold to navies overseas, including Argentina, Australia, Ghana, India, Ireland, Malaysia and South Africa.

It is estimated that in their history some 3,200 officers and 28,000 ratings served in Ton-class ships.

The Ton-class Association has 1,200 members, and it has been closely involved in the seminar.

The Association is compiling a detailed record of service for each ship of the class, some of which saw 30 years service in the Royal Navy.