I was involved in the AST 412 competition when we evaluated the PC9, Tucano and Firecracker at what was then British Aerospace at Brough. We eventually chose the PC9 as our preferred candidate to support and were quite happy with the Pratt and Whitney Canada PT6 engine. However we had several visits from Garrett trying to persuade us (and Pilatus) to change to the TPE331 before the design was finally submitted for evaluation against the RAF's AST412 requirement.
We were very disappointed to lose to the Tucano and quite surprised when Shorts changed horses and decided to go down the Garrett route instead of the PT6. I was even more surprised several years later when one of the senior officers involved in the AST412 evaluation visited Brough as the UK rep for Garrett.
Walbut