You basically asked the same question back in 2019 and @JaneJones gave you advice on what to do. Did you register for tax in France and get the CdS as Jane discussed with you ? If not, then you are in a tricky position as you will be living in France illegally. If that is so, then I’m not sure what you should do, and trying to get an S1 under those circumstances will probably not be possible. If you did do those things, then you’re fine and can and should apply for an S1 as it should not affect any UK pension you may be receiving. As you say you were 73 in 2019, you could have done this as soon as you became a French resident.