I needed a wheelchair at Heathrow a few years ago. There was a holding area where they put people waiting for wheelchairs and then someone would come get you when the gate was announced. The odd system at Heathrow is that the gate is not announced until very shortly before the flight, and then you have to get to the gate which can be a pretty long distance away. There are ways which involve elevators instead of stairs for the wheelchairs.

There are also electric carts. We were lucky that a lady driving the electric cart jumped through hoops to get us to our gate in time, as our arriving flight on the way back through Heathrow was late.

In any event, distances at Heathrow can be huge, and it is better to use the wheelchair or electric cart if your mother has trouble walking distances quickly.

Wheelchair assistance if you DON'T carry your own wheelchair is done through the airline you're flying on. FYI wheelchair assistance is often NOT right at the gate when you disembark so you want to make sure your mom has plenty of time between connections.

My husband and I used wheelchairs heathrow treminal 5 last year. They were right there when we got off the plane and they took us thru the airport, which is enormous, so fast that we were the first from our flight thru passport control. Just one example, I hope you are so fortunate. The terminals are so large that wheelchairs or electric carts are a necessity for many.

FYI wheelchair assistance is often NOT right at the gate when you disembark

In my experience it's never like that at LHR.

Confirm, confirm, confirm that the wheelchair or other assistance is actually reserved.

And tell you mom and brother to be sure to ask the flight attendants if their names are on the list for the electric cart and/or wheelchair when they first board the aircraft to LHR.

Back in the fall I sprained my ankle before a trip to Europe and thought I might need assistance in LHR. I called the airline to request it (Delta in my case), made sure it showed up in my reservation online, and even re-confirmed it when I checked in for the flight in the US.

When I arrived in London, I was told my name wasn't on their list for people needing assistance! There was a cart waiting at the gate for people needing assistance, but it was full. The airline personnel at the gate told me I could wait for someone to come get me, but eventually I just gave up and walked to immigration.

I don't know if speaking to a flight attendant when I boarded would have done any good, but I think they usually have a list of who needs assistance upon arrival.

Call AA or BA or whoever you booked your ticket with if you used a travel agent, ask for wheel chair assistance for the whole itinerary. When checking in at your orgin, the check in agent should see a note on the reservation that your mother will require wheel chair assistance. Make sure you tell the check in agent she will require wheel chair assistance at the transit airport/destination too. If everything goes smoothly you'll have nothing to worry about.

Thanks all for your kind and thoughtful advice. Wheelchair has been booked; and it should be interesting. They do have day passes for the admirals club; I'll be very iterested to see how it plays out!