Originally Posted by
corporate-wage-slave
In theory the night before departure, to give time for full ticketing, but you probably best add on a few more days.
However I would advocate people are realistic about their travel plans, given the changing situation. Cash in the bank is very usable, FTVs less so.
I have my flight transferred from LGW to LHR, called BA and confirmed that cash refund is not available. Only FTV in this case.