Was the OP on a split ticket or did he have a schedule change that he failed to resolve. DL895 was scheduled to arrive in at 8:40pm but arrived early at 8:24pm. The last Delta flight of the day from ATL-LHR appears to be at 9:23pm, though I can't see any flights operating on FlightAware for March 18th. Delta.com does not let you book SJO-ATL-LHR using DL895, you have to take the earlier 1pm departure out of SJO.

The OP did tries to make it sound like he planned really well by booking him into LHR the day before. Booking the last arrival of the day with a tight connection when you have an extremely important meeting at 8am the following morning is not good planning.