Complex sentence: Their activities were monitored and by early March, the British authorities were convinced that an IRA attack was imminent; a special projects team from the SAS was despatched to the territory, apparently with the personal approval of Prime Minister Margaret Thatcher.
Split into simpler sentences: Their activities were monitored, and, by early March, the British authorities were convinced that an IRA attack was imminent. A special projects team from the SAS was despatched to the territory, apparently with the personal approval of Prime Minister Margaret Thatcher.