Would Civilian Internees been on working outside of the camps?

[Ralphed]

I have come across a pic that is of a road gang working party. It's connected to Friern Banet web page http://www.friern-barnet.com/picture/number6844.asp

What's strange about the pic is that two of the men are in military uniform circa WW1. The one that's the clearest is wearing an ammunition bandolier which would suggest that he has a weapon of some sort. Would internees be put to work under armed gaurd? Ally pally was an internment camp and is not far away from Friern Barnet.

Any thoughts ?