Complex sentence: The first Westland-built Wessex "XL727", designated a Wessex HAS.1, first flew on 20 June 1958, and they entered anti-submarine duties in 1961 with the Royal Navy Fleet Air Arm.
Split into simpler sentences: The first Westland-built Wessex "XL727", designated a "Wessex HAS.1", first flew on 20 June 1958. The type first began performing anti-submarine duties in 1961, operated by the the Royal Navy Fleet Air Arm.