Originally Posted by
Steve M
I would imagine that you could change the dates of BKK-LHR or LHR-STO under the "free changes with no reissue" rule, and then pay the LHR departure tax upon check-in (or not if they don't catch it at that point).
Provided, as pandaperth said, the OP has not already made two stop-overs in Europe - their continent of origin and thus whilst four segment can be flown, only two stop-overs should be allowed. The OP doesn't say what they did at the start of their DONE4 so we can't tell. Not sure if anyone has tried and succeeded in getting away with a date change to sneak another stop-over in.