In response to customer demand, passengers departing from T4 will now be able to experience the T5-style delights of going up and down staircases, lifts and escaltors for no apparent purpose, just for the hell of it:

https://www.britishairways.com/trave...b?p_faqid=3373

All customers departing from Terminal 4 arriving by car should:
continue to be dropped off at the departures level
take the car park lift down to arrivals
enter the terminal
....take lift or escalators up to arrivals

All customers arriving into the terminal by public transport will be unaffected.

And in further response to customer demand, we will make it even more confusing for our passengers, by directing them to the Departures level, from where they will be directed down to the Arrivals Level, from where we will send them back up to the Departures Level, except - and here's the cunning bit - we tell them to take the lift or escalators up to arrivals, when we mean departures.

Unfortunately for our customers, BA.COM seems to have blanked out the word f***ing from the line take lift or escalators up to arrivals, which we thought would help them flow through T4.