Flat Wagons

Me again with another awkward question! Does anyone know the wheel diameter of the bogie 'flat' wagons built for LT in stages from 1931? I am after the diameter of the wheels as built with diamond-frame bogies although I doubt that it changed when the wagons were refurbished. I know that some measurements are included on a couple of boards pictured with a new wagon when built. The picture was published in the last chapter of 'Red Panniers' but I cannot find my copy of the book anywhere!

Thanks once again.