Does anyone have any idea on what the minimum turn around time would be on a back to back LHR-IST run to start a DONE4? Depending on the time of year, you can get up to 1 1/2 hours in IST. Would this be enough time to get through customs and then check in to catch a flight back to LHR?

Here are some example BA flights:

July:

Out
LHR-IST Dep 09:55 Arr 15:40 BA 676
Return
IST-LHR Dep 17:10 Arr 19:10 BA 677

Turn around time above = 1hr 30 min

December:

Out
LHR-IST Dep 09:50 Arr 15:35 BA 676
Return
IST-LHR Dep 16:30 Arr 18:40 BA 677

Turn around time above = 55min

Any insight would be much appreciated.

QH