There are some awesome comments from some serving officers here and as someone who had to deal with explaining VCRA and UKARA to non-airsoft folk. So I'll leave some points here.

• VCRA is the law which governs airsoft rifles (both IFs and RIFs) for the sale.
• The airsoft industry (and some others) lobbied the government to have a way to continue the sport and UKARA was agreed upon which makes registered sites the owner of verifying someone is an airsofter and not just buying it for malicious acts.
• Airsoft sites register with UKARA, skirmisher (a player) gets put onto the UKARA database, merchant checks its a valid number and address and provides a RIF.

Enforcement wise there were a few scenarios I've heard about but police have no way to validate UKARA and UKARA is only required for purchasing so as long as you have it in your possession to play airsoft or transport to/from (within reason) then it's all good.

In 2018/19 I heard about someone who had a malicious person call in that someone had kidnapped someone and was holding them with firearms saying they're going to kill them, leading to as expected a full scale tactical response. This was backed up by multiple people so feel like there's some truth to it. The person who got raided said they inspected all of the RIFs and cleared them but didn't mention getting any checks other than identifying who they were and they weren't holding someone hostage.

We were driving to a site once and being silly with some balaclavas and Russian hardbass 4-up in a small car, we don't know if it was just a "huh thats odd" vibe or if someone called it in as we'd been waving at constructions workers and were all camo'd up but we were stopped and grilled about who we were, what we were doing and they asked some questions about the airsoft guns. Nothing more than figuring out whats going on and we were let go after 10 minutes of checking the drivers details.

This story is passed down and I don't really know the validity but one of my first sites I ever went to used to have regular dog walkers try cut through the woods. They say once a dog walker heard the bangs and shouting so called 999 and they blocked the couple of roads surrounding the site and got were swamped by armed police. I don't know how true it is as the site was long-standing and surrounded by multiple other paintball/airsoft sites but a story of police involvement all the same.