re: “Major” incident thwarted in the UK. USAF base targeted

I think people might be conflating two separate statements. Yes, we might be tracking SOMEONE. An RAF base doesn't go to alert Delta without a credible threat. That doesn't mean these guys were the ones being tracked. Their quick release kind of lends credence to that thought.

If you are tracking a threat, you don't let it get within a 100m of the base and depend on some farmer returning from town to call it in.

Alternatively, they could just be patsies used to probe the base's defenses with suspicious but ultimately non criminal materials. Hey guys, just drive up there and look suspicious and see how long it takes them to react kind of thing.