This is a bit niche, for avgeeks mostly.

There's a 25% refund on buyagift on amex cards - this was from a week or so ago I think. This stacks with a 14 avios per pound spent promo in the e-store.

Why is this of interest? Because buyagift is an experience reseller, and one of the experiences they resell is a 70 minute flight in a Dragon Rapide sightseeing over London, from Duxford, for £255. You also get entry to the collection at Duxford which is well worth a look. There is also a 150% price difference promise if you don't use vouchers, and ClassicWings sell the same package for £26 less (£229), so in principle a further discount of £39, but I haven't tested that yet. There are some vouchers floating about too, you automatically get one for £10 for signing up in the first place.

So the result is a very substantial discount on something that looks like a lot of fun. You get a voucher to redeem for pretty much when you want as far as I can see, and there's also a 60 day refund policy. If anyone else signs up let me know and it may be possible to coordinate something. The Amex offer triggered immediately, and the e-store tracked the next day for me.