Newer krytos lock both ends of the shackle which is nice. There's also something called litelok x1 or something which is apparently very hard to saw through. Costs 150 tho.
Maybe keep it for the front wheel? Downtown, an additional kryptonite mini7 or Evo through the frame and rear wheel, depending on how much you don’t want to lose the bike. Also bearings glued in the stem etc bolts.
What’s the current lock/locking combo of choice these days in London? Not sure my ten year old orange kryptonite is up to standard now.