I'm on the way to meet German national friends for coffee, who are going to Hawaii from HAJ via LHR. They've arrived in Heathrow terminal 5 and took an airside bus to T3. They've gone through a US pre check and another security checkpoint when they arrived in T3.
We now worry that we can't meet for coffee because they can't get out any more and will be stuck in there for a few hours.
Can they get landside from the US departure are in terminal 3? If so, how?