For HTB's benefit.
When 29 Sqn (along with other squadrons taking up then unofficial squadron schemes) adopted its"X" 's on its Grebes in the mid '20's the number was indeterminate, the primary marking being a line of diagonal crosses -probably three in total ( not letter X's incidentally ) across the upper wing with some repeated on the fuselage.
As dave f68 pointed out, four of these crosses were certainly marked on some of the Grebes. This fact along I think satisfactorily demolishes the XX, one X fable.
The number of crosses was certainly six across the wing in at least some Siskin IIIas photographed in the late 20's , with the broad chord of that wing allowing them to be made quite sizeable. Three crosses either side of the fuselage roundel was also normal.
Apparently with the introduction of the Bulldog into the squadron in 1932, the number of fuselage crosses dropped down to one either side of the roundel.
As noted a single X has also been photographed either side of the fuselage roundel on a 29 Demon in 1935. which knocks down the myth of XXX having been strictly adopted in the late 20's.
Post WW2 the three crosses either side of the fuselage roundel came to be standard on the fuselage bars of Meteor, Javelin and Lightning etc.
My interest in all this only came about when meeting( and once flying with) 29Sqn in their Lightning days in the 60's .
Last edited by Haraka; 1st Apr 2014 at 15:19.