They were designed to be launched from slipways or operate in shallow waters where hitting the bottom is a concern.

Following completion of the test programme, City of London entered service at Selsey in November 1983 while Sam and Joan Woods was put into service in the relief fleet in 1984, by which time the first production boats were under construction.

The Tyne also lies afloat at stations where the approaches, or operating areas, are particularly shallow.

As the lifeboat's propellers are protected by heavy bilge keels, she is particularly well suited to operate where there is a danger of hitting the bottom, or tapping as it is known colloquially.

Later, further doubts about the self-righting capability resulted in air bags being added to the aft cabin roof.