He also quotes Mr. Cox as saying: "they were, however, glad to avail themselves of S.R. knowledge of steel firebox stays," but that could not apply to the "Nelson" class, the first six of which had boilers with copper stays and the remainder stays of monel metal, as far as I can remember.
1947 January and February, H. Holcroft, “"Castles", "Lord Nelsons" and "Royal Scots"”, in Railway Magazine, pages 13–14