Complex sentence: In 1929 the airfield at Cricklewood was closed and a new one built at Radlett where most aircraft were now to be constructed however the construction of aircraft at Cricklewood continued until 1964 when the premises were sold to become the Cricklewood trading estate.
Split into simpler sentences: In 1929 the airfield at Cricklewood was closed and a new one built at Radlett, where most aircraft were now to be constructed. However the construction of aircraft at Cricklewood continued until 1964 when the premises were sold to become the Cricklewood trading estate.