Heightened taxation following the First World War meant that many professionals could no longer afford to buy larger houses and villas. Consequently, speculative builders rapidly purchased land and constructed more modest houses, causing rapid expansion of the built-up area of Colinton. Edinburgh argued that since it already provided services including water, sewage, gas, and electricity, these would be more readily extended and more cheaply supplied if Colinton became part of the city. As such, the parish was amalgamated into Edinburgh in 1920.
Just before and during the Second World War, the military presence in Colinton again increased with the construction of the Dreghorn Barracks in the grounds of the 17th Century Dreghorn Castle. In hosting both the Redford and Dreghorn Barracks, Colinton effectively became the ‘home of the army in Scotland’. Since the war, Colinton, whilst being an affluent part of Edinburgh with a very diverse population, has retained much of its village character making it an attractive place to live.