MARGARET THATCHER ordered the Royal Navy to land Special Boat Service (SBS) frogmen on the coast of Sweden from British submarines pretending to be Soviet vessels, a new book has claimed.

The deception involved numerous incursions by British forces into Swedish territorial waters in the 1980s and early 1990s, designed to heighten the impression around the world of the Soviet Union as an aggressive superpower.

Sometimes the boats landed commandos, but often their job was to fool the Swedes by mimicking the sonar signals given off by the Soviet vessels that stalked the same waters.