With two of five daily flights JER-LGW per day arriving before 10 am and, barring major catastrophe, the coach transfer never taking more than two hours, given the two latter IAD flights depart LHR at 14.35 and 17.10, I find this statement incredible.
Fair comment ... however, my planning is predicated on taking the 1050 departure, arriving IAD 1340. I have an aversion to arriving later in the day, or driving round the Beltway in the dark, after a TATL. By the time we've got some grocery shopping done, and had something to eat, it's time for sleep!
It's a long day at my age!!