It would be interesting to see the business plan for SHL airport.
I cannot see it paying back GBP 250M ever if the revenue is just from tourism and obviously there are other costs than the airport associated with that.
The only other source of revenue I could see was from Satellite uplink operators who want to take advantage of SHLs favourable position for uplinking data to S America and Souhtern Africa. Once again though this is dependent on spend elsewhere and the airport bit is only to allow hi tech equipment to be shipped to the island and to send specialist techies to and fro .
So I cannot see how it would have ever made money even if in this case a profit is actually just a reduction in UK subsidies. A very sad story