In the past I have use an infra red lamp with night vision scopes, but it is fiddly, so this time I tested out the simpler approach of using a red lamp. They did not seem bothered by it, and we watched a family for around 30 minutes. The camera shutter, even on it's quietest setting caused the most alarm.
An adult emerged at 21.43 and snuffled around in the undergrowth, then nearly 10 minutes later 3 cubs and another adult appeared. The cubs stayed close to the sett entrance.