And just to and any airside transfer to/from T4 is not great atm. The cargo tunnel which is an airside tunnel connecting the central terminal area and T4/cargo is currently closed for refurbishment. This tunnel is used by the airside buses which go to/from T4 to T2/3/5.

The impact to the closure is that the only airside buses running to/from T4 go to T2 - there are no direct airside buses from T4 to T5 or T3. The airside buses take a long and slow overground route now between T4 and T2 which goes around the eastern edge of the southerly runway. Unless the work has finished by next week the op would therefore get an airside bus from T3 to T2, then wait for another airside bus to T4. On arrival to t4 the op would go through security and then in to the airside departures area.