Transfer security at Heathrow

No, providing you don't have to change terminal.

Frank,

It's been a while, (my most recent trip from Leeds to Heathrow has been a few years...maybe 4-5), but at that time, we had to go through the same security as we do when we fly in from another country. This was/is in Terminal 5 and remaining in Terminal 5.

You must have gone unknowingly through Arrivals rather than connections. Easy to do especially if arriving from a remote gate by bus as you need to go upstairs.

The domestic gates are A1-A3, or A5-A8. You enter the main departure area by going through a boarding pass checkpoint situated opposite A5.

I've been going thru this airport, Terminal 5, for 20 years? (since it was brand new) and I've never not had a security line...but often, lately, I'm flying thru, which is different than Frank asked about. So...maybe it is different now? Although, domestic always sent us through the same security posts as when we were international connections and it is not the one we go thru when we arrive to the airport from out side the airport. So dunno...

I thought all flights to the US required a new security check, regardless where you started. But I just ran flights from Manchester to LHR to JFK through the Heathrow Flight Connections planner and they do not show a security check.

Anyone connecting off a flight that originates in the UK or the Crown dependencies does not need to go through security again, provided they can avoid co-mingling with passengers from elsewhere. Some airports make the latter condition impossible from their configuration but not at Heathrow providing it is within the same terminal. Only T2 and T5 deal with these UK/CD flights.