Today the Territorial Army turns 100. Formed on 1 April 1908, the force first mobilized in 1914. The recruits shown here are outside Somerset House, London, in August of that year.
Territorial units were demobilised in 1918, then reconstituted in 1920. Seen here in 1928 leaving for the year's highlight - a two-week summer camp where their skills were tested.
On the outbreak of World War II, the TA was mobilized and absorbed into the British Army. All men had to report for health tests as soon as they were called up.
Many women served in the TA during World War II through the Auxiliary Territorial Service and the First Aid Nursing Yeomanry.
An ATS (Auxiliary Territorial Services) girl of the Eastern Command washing dishes while wearing her gas mask during a refresher course of anti-gas training on 1 April 1941.
After World War II the TA was again disbanded and before being restructured in 1947. Military vehicles, like this one outside St Paul's Cathedral, were used to entice new recruits.
But during the 1950s and 60s, when this young recruit was volunteering, the government allowed the TA to become under-manned and ill-equipped.
In the 1970's the government realised the error of letting the TA atrophy and began recruiting. Here 19-year-old Miss Great Britain, Wendy George, joins the effort from a parachute training tower.
By the 1990s the regimental system was almost totally re-established. But throughout this period of fluctuations the TA was never regarded as a particularly effective force.
The TA's role is also to step in at times of national crisis, such as in 2003 when the military Green Goddess fire engines were brought in during a 24-hour fireman's strike.
The TA are now being relied upon more heavily than at any time since World War II. Nearly 15,000 Territorials have served alongside the regular army in Iraq and Afghanistan since 2003.
Five TA members have been killed in Iraq and three in Afghanistan. They face particular difficulties when they return as they come back to civilian life without their comrades.