New plug spanner arrived today and it fitted!
O/S diameter is 21.6mm as opposed to the one that didn't fit at 22.8mm.
That's a difference of only 1.2mm, but it made all the difference!
Not started the engine up yet, maybe later.
......................................................
Next question:
Now I have the old plugs out, I see they are numbered 55233997
New plugs from Shop4Spares is 55242187
Does this make any difference?
They are visually identical.
Also the old plugs have a spark gap of 31thou (as measured with my elderly feeler gauges) and the new ones at 25thou. Hopefully, the difference is because of the old ones having done 18,500miles.
Anyone like to comment on the new plugs?
Thanks,
Mick.