Could mean anything, Nibbler.
An aircraft could easily have been in that position (close to base/final turn) if they wanted an overhead departure and ran into problems before departing the circuit, or if they had problems shortly after takeoff and were trying to get round the circuit for a precautionary landing, or all sorts of reasons.
It is to be hoped that the AAIB will find something that can be published and serve as a warning to others, but I think it's unlikely.
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