I've flown into London like four times but the amount of time I've actually spent in the city that wasn't Heathrow or the inside of a cab on the way to somewhere that was not London is actually 0 hours, 0 minutes, 0 seconds.

You can get to the Natural History Museum or Design Museum via Underground direct from Heathrow. Both have cool exhibits. If you want to know about "only in London the week I am here" stuff, follow @londonist-rss.bsky.social@ianvisits.bsky.social for special goings on.