T1 has already started in a fashion with the closure of outlets airside such as Starbucks and TieRack. Work will be done in stages and according to a meeting I was at recently will take two years. If you are a wheelchair user, have mobility problems or have babies in prams and buggies, T1 departures may well be a bit of a struggle for you til the new escalators are installed airside where the café is currently situated.