Stay out of sight if possible, observe them and make notes to help the police:

Details of the people involved; their height, build, hair colour & cut, clothing, distinctive features.
Details of their equipment; spades, sacks, nets, dogs.
A description of what they were doing; digging a hole, filling in a hole, etc.
Anything you have overheard them saying, especially names and anything relating to badgers.
If you have a camera and can turn off the flash, take some photographs of the scene.

If you are seen, or have to pass near them to leave the area, don't stop or ask what they are doing.

Act naturally; stroll past and away then look for their vehicles and note make, colour,registration numbers.
If you have a camera and can use it from cover, take a video or photographs of the men.
Take useful notes of their descriptions and actions to help the police if possible.

Call your local Police Wildlife Officer if you have the number, otherwise 999

If possible, also ring the RSPCA.
Give clear instructions on how to reach the location or arrange to meet them at a nearby landmark if necessary.
If the police and RSPCA arrest and prosecute the culprits, the notes you make at the time will be vital to the case.
Make sure that you record the event clearly and make detailed notes of everything you see.
If you return to the scene with the police, continue to make notes.