I have a very long layover in T5 and I was thinking about killing some time by taking the airside transfer bus to T1, T3 and/or T4 (with the intention of touring the other terminals and OW alliance lounges).

(I know at one point you could also walk between T1 and T2 (down a side area), but of course this is no longer possible!)

I did this transferring a few years ago and had no problems - they didn't seem to care - but wanted to check whether this is still possible, or if they are stricter now about making sure that supposed connections match up with boarding passes these days?

Thanks!
CD