Whilst the horse wasn’t just owned by the Aga Khan, but in fact a syndicate of many shareholders, this episode focuses on one shareholder that had a lot to lose. Stan Cosgrove. The Vet.
He was keen to get his insurance payout, but the only way to do so was to prove that Shergar was in fact dead. Coordinating with the kidnappers he organised to get a polaroid to prove the horse was still alive.