After two years of pilot training, Mussell was granted a permanent commission[1] and appointed to be aide-de-camp to Sir Robert Tredgold, the Chief Justice and acting governor of Southern Rhodesia.

On completion of his staff training he served at the Rhodesia Air Force headquarters in the operations branch before gaining a promotion to wing commander and taking up appointment as the director of plans (air) on the Rhodesian Joint Planning Staff.

In 1966 Mussell was sent to Lisbon, Portugal, where he joined the Rhodesian Diplomatic Mission as the first secretary (political).

He returned to Rhodesia at the end of 1967 to take up post as the officer commanding RRAF Thornhill with a promotion to group captain.

Mussell was replaced by Air Marshal Norman Walsh,[2] Robert Mugabe's appointee.