Complex sentence: The longest serving Squadron was No.631 Squadron (RAF) who arrived at Llanbedr in May 1945 from RAF Towyn and stayed until February 1949 when the Squadron was re-numbered as No.20 Squadron RAF.
Split into simpler sentences: The longest serving Squadron was No.631 Squadron (RAF) who arrived at Llanbedr in May 1945 from RAF Towyn and stayed until February 1949. The Squadron was re-numbered as No.20 Squadron RAF.