Conversation so far:
How did Ross Brawn's career get started?
His career in motorsport began in 1976 when he joined March Engineering in the town of Bicester as a milling machine operator.
How did he do there?
Soon afterwards he joined their Formula 3 racing team as a mechanic.

Question: How long did he work as a mechanic?
Self-contained rewrite: How long did Ross Brawn work as a mechanic?