Spearhead was a 1978 TV drama that provided an unglamorous worm's eye view of British Army life from the soldier's perspective. The story revolves around a platoon in the fictional 1st Battalion Royal Wessex Rangers, designated as the Army's 'Spearhead' battalion. Series 1 was the best and see's the fictional squaddies undertaking an Internal Security role in Northern Ireland. Plenty of Winter of '79 eyecandy in the form of Humber Pigs and armoured Landrovers.
Light infantry battalions in the UK were assigned in rotation as a rapid reaction 'Spearhead Battalion' capable of short-notice deployment worldwide. It required the chosen unit to be ready to deploy its headquarters, lead ('active edge') company and logistic elements within 24 hours and have the remaining companies and support assets on the ground within 72 hours (source: Hansard).
Spearhead: episode 1 (fast forward to 2:10)
A Spearhead Battalion may have familiarisation deployments in Belize, Hong Kong, Cyprus and Kenya prior to taking up it's spearhead role. The most common operational deployment was short notice contingency reinforcing of British troops in Northern Ireland in antincipation or response to crises.
To ensure the troops were at the highest possible state of readiness, the Spearhead Battalion was issued with full scales of wartime equipment and undertook regular sub-unit exercises and readiness call-outs of the lead company. The Lead company was expected to maintain a permanent maximum 4 hour alert status.
Today the Spearhead Battalion is known as Spearhead Land Element. This assignment lasts 4 months and the 'active edge' company is expected to deploy within 24 hours with follow up elements 4-12 hours later.
In Winter of '79, the 'Spearhead Battalion' provides us with a highly trained and efficient rapid reaction force that can be used at flashpoints anywhere in the country.