'relieving myself' of responsibility

ok - so im drowning in details at the moment - hang with me

"One member of the team, using the call sign Tango Ten, began watching the flat at 6.30am. A soldier who had been with the Met for a year, he was equipped with a mini-DV camera which was not permanently recording in order to conserve its batteries. His job was to film people entering and leaving and then compare them against photographs of the suspects...

When Jean Charles de Menezes left the block, the soldier was relieving himself and unable to turn on his camera.

His log report reads: "As he walked out of my line of vision I checked the photographs and transmitted that it would be worth someone else having a look ... I should point out that as I observed this male exiting the block I was in the process of relieving myself ... At this time I was not able to transmit my observations and switch on the video camera at the same time. There is therefore no video footage of this male." At this point there were two surveillance teams around Scotia Road and a firearms team on standby nearby." (link)

is it standard practise when there's a terrorist attack with 3 teams on hand, and "shoot-2-kill" in place, to be worried about conserving batteries? and not having a backup plan when someone needs to urinate? (i read somewhere that he was peeing behind a nearby tree). surely this is nonsense. i just wanna know why.