Letter: Electric currents brought prison ship to Portland

Sir: The people of Dorset having to accept a floating prison moored in the harbour of Portland may be an unintended consequence of Britain's decision in the 1940s to become a member of the North Atlantic Treaty Organisation.

One of the conditions of joining Nato was that all ships would have a uniform electrical supply system. As the major financial contributor, the USA persuaded the other members to build all future fleets with 440- volt 60 cycle per second alternating current supply systems. The significant thing is the 60cps stipulation. It is not too difficult to convert voltages, but very expensive to convert frequency; and the British National Grid works on a frequency of 50cps. Most electrical equipment is frequency conscious: 60cps equipment will not adequately run off 50cps supplies.

The Royal Navy went to the expense in the 1950s of building shore power stations in the Royal Naval Dockyards to provide power to its own and other Nato ships in port. These ships cannot be supplied or serviced in any other British port, because the electrical supply is incompatible.

With the ending of the Cold War defence cuts meant that some RN dockyards became redundant, including Portland, and to date Portland has not found an alternative role for its dockyard.

In 1997 the Conservative penchant for imprisoning citizens created a need for emergency prison accommodation and procurement was made in the USA. The newly acquired penitentiary is American-built and so almost certainly equipped with 60cps electrical systems, without which it is uninhabitable.

The only place in England and Wales that is sparsely inhabited and unemployed and boasts an adequate electrical supply is Portland: no amount of public inquiries will change this.

J K MEREWEATHER

Paulton

Bath and North-east Somerset