Officer orders lane to be diverted round square

Wiktionary Word definitions in Wiktionary
n. A rank in the RAF, between that of flight lieutenant and wing commander, equivalent to an army major

Wikipedia Word definitions in Wikipedia
Squadron leader ( Sqn Ldr in the RAF and PAF ; SQNLDR in the RAAF and RNZAF ; formerly sometimes S/L in all services) is a commissioned rank in the Royal Air Force and the air forces of many countries which have historical British influence. Squadron leader ...