Yes it is 100 metres but don;t forget you are in the departures area and can't just walk back through where you came from check in. If you are 'landing' then you need to go through the proper channels back to immigration, hence the long way round to go what is a short distance in reality.
Well aware of where I am and the legalities but it's still a bloody long walk
Having 1000 pax descend on anyone at short notice isn't the easiest thing to handle at the best of times.
which explains why they had 20 mins to get themselves organised yet couldn't.
I've no doubt I'll have to travel through the place again despite my (foreign) boss trying to ban me from using BA however I'll seriously consider waiting landside until the 35 min deadline if there's any doubt in my mind that the flight'll be going.