T1 Domestic to T4 in 90 mins - no problem.
T1 Int'l to T4 in 90 mins - could be a problem, depending on how backed up FCC security is. Last month it took me nearly 50 mins to clear security there even with the use of the "fast track" lane. The lines were backed up to passport control on one side and the Euro pier on the other side. I nearly missed my LHR-NRT if I hadn't squeezed past a lot of people in behaviour usually unknown to me !