@Steve ******
Interestingly, I just went and checked. That cover specifically cuts off at 31st March.
There is a multi-risk policy that pre-dates it though for flights booked between 21st December 2020 and November 30th 2021 so it looks like that one is a fit for me.
My only thought there is that I changed the flight to HKT rather than BKK because it seemed like a safer bet. I've emailed the insurer to find out and get the policy.
Hope all this fluffing around is worth it :)