Dozy, not off thread, wonderfully ON thread to straighten some of the wonky lines that people have been shooting in here.
I am sorry that PBL cannot continue (for whatever reason) and, whilst remaining fascinated by this mystery, I think that I shall wait the results that RTFM has kindly calculate at 25.6 months. My thanks to RTFM for that, it confirms what I have said so often.
Many can now draw a sigh of relief as I leave this thread to it's natural end ...