Seat pillar size for my Claud?

Got a 1969 Electron. Every post I have is 27.2 which doesn't fit,any idea?

When I say doesn't fit it's very very close.

My experiences with the Holdsworthy Company (owners of F Grubb, C Butler & Holdsworth names) finished in 1966.
If your frame is listed as 531, I presume it is plain gauge, which would be 20g. This would take 26.8mm. Butted 531 would be 23G at the top of the seat tube. It could be grade A tubing, as they used a lot if it. If you measure the inside diameter beware of distortion caused by brazing. In the time I sold them I never saw one built with the very cheap seam welded tube, as used by Raleigh (Tru-Wel).

These Clauds were just plain old tubing, there's no reference to it being Reynolds. The frame did have a Prugnat? transfer though.
Cheers.

I thought the tubing commonly used by Holdsworthy was drawn Reynolds grade A, as used in the early 30's before 531. It used to be stamped A on the ends of the tubes, which would be cut off or under the lugs.

You should not be able to feel a seam with a finger down the inside of the seat tube.

Most makers using poor tubing invented wonderful names for it. Peugeot had "carbolite 103" , raleigh had a number of well documented names.
Remember bikes had to be made down to a price.

If you consider the size of the lightweight bike market in the UK in 1962, my 1 man shop with a Saturday assistant had the largest retail accounts with both Ron Kitching and Holdsworthy in the South of England.
I sometimes bought spokes in excess of 100 gross lots. I could lace up (loose) a 40 hole cheap wheel in 3 minutes, a new 5 speed freewheel and chain I would expect to fit in 10 minutes.
I'd rather not be reminded of all this I think.

It might be, I just assumed it was no name tubing. Though I am impressed with it, it's down to bare metal and just peeking inside the tubing the finish is excellent.