 In a letter to the aviation magazine "FlyPast" a retired RAF Sqn Ldr states that his aircraft (Avro Shackleton Mk.III WR981) was the 'Object' tracked by the various radar stations, and the incident was part of a much larger TACEVAL (station TACtical EVALuation) exercise.Two Lightnings were involved.The first made four approaches on the Shackleton, before departing the area while the second started an approach (flown by Capt Schaffner), before breaking off to Starboard.