My google page speed stuff I had been doing to speed the page up had broken things. One of the page speed rules is "move all your scripts to the bottom of the page", and it is scripts that was serving the ads. I was doing this automatically and had not spotted it. Fixed now!
Paulʼs weblog - I live in A sleepy town in Kent. Wed + father to two, I am a full-stack web engineer, and I do javascript / nodejs, some ruby, python, php ect ect. I like pubs, running, restaurants, home-automation 🤖 and other diy jiggery-pokery, history, family tree stuff, TV, squirrels, pirates, lego, and TIME TRAVEL.