I'm wondering if I should check out the jug capacities. The Lancer pint tankard is indeed 5in. tall, so I would expect the Britannia to be similar. However, it could be that the Britannia jug, with a higher top edge and a lip is taller because of this. Also, you never fill jugs to the brim, but you would a tankard (before measured marks were introduced on over-sized glasses).
Ming, I can't put my hands on the Britannia 'pint' jug right now, but it should be just under half litres if you have no imperial measure to hand.