The difference that Carlin was making (I listened to this podcast myself) is that while yes, the French and German armies were also "professional", the British army was a Volunteer Army. Whereas France and Germany conscripted and drafted basically most of their armies, Britain's army (at least in 1914) was composed of volunteers that joined on their own accord. These volunteers then usually stayed in the army for long periods of time, whereas conscripts and draftees in Germany and France were allowed to leave military service after they served their X-amount of years of required military service. As a result, Britain formed a small, but very well trained army. The average quality of a British "regular" at this time was on par if not exceeding of the average French or German conscript.