The Ffestiniog's track gauge is generally quoted as 1' 11⅝", which is extremely close to 600 mm. Wikipedia quotes both the WHR's and the L&B's gauges as 1' 11½" or 597 mm. The gauge of some other railways is 2', i.e. 610 mm. Acknowledging that any track gauge figure is nominal, affected in practice by considerations of tyre profiles, widening on curves, etc, the above figures nevertheless prompt some questions. Are they actually correct? How did the Ffestiniog's gauge, a nice round number in mm and not a nice round number in inches, come about? Are the WHR and the L&B indeed ever so slightly different from the Ffestiniog, and if so why? As the original Garratt was built for a 2' gauge railway, what if anything had to be done to its tyres for running on the WHR?