Of course, the job of the guards is to keep villains and knaves out of town—to maintain order. Although it was not expressed in the Ultima computer games, one might expect this duty to also extend to the patroling of major roads. The guards of Britannia can easily be represented by the "Human Warrior" stats in the wargame I'll be using, Song of Blades and Heroes.
The guard captain has been painted with an ankh on his surcoat. This is the symbol selected by the producers of the PC game to represent Britannia's philosophy of virtues put forth in Ultima IV. The ankh was a good choice. It's a good looking graphic, and no one was is likely to be offended by it's use since there are no living polytheist Egyptians these days. The serpent emblazoned on his shield is another symbol from the Ultima series. I think it's supposed to be the "Silver Serpent," but I don't know the significance of that.
My guard models are sold by Black Tree Design. They are from their Hundred Years War range: HYW1004 Infantry with Halberds, and HYW1001 Foot Knights with Swords. Black Tree has some nice models, but their customer service has a spotty history. A read through the messages on TMP will reveal complaints of missing or long-delayed orders, lack of communication, etc. Problems are usually worked out in the end, but not without hassle. I live in the US and have ordered from the UK location twice. The first time (maybe '05) my order went missing. After some complaint, months later I received a replacement box at no charge. My second order (summer of '07) was missing some models. It had been the case that all Black Tree models were produced in England, but there is now is US location in Texas. My advise would be to order from within your own country, or (even safer) buy from a dealer in person).