I stopped flying back on Ryanair late at night. Far too often planes were late back (having maybe lost a few minutes on each flight) and if a number arrived at the same time, it seemed you had to wait for your bags to be taken off - which could be up to an hour.
In some respects, the slow progress through passport control wasn't such an issue if you had bags as it killed some time. For those with hand luggage, it would be very frustrating.
It was also quite likely that anyone wishing to take the train to Liverpool Street would miss it if they came in on a late plane, as you'd have to add an hour to the already delayed time, meaning you'd now be stuck on a coach.
Obviously by not doing this anymore, I have no idea if things have improved. I have flown earlier in the day and the passport queues are still there, and they were installing machines that seemed far slower than the ones I used in Germany (which scan your passport while you're waiting for the person in front, given it takes up to 10 second to read the data off the passport). Staff were already slagging the new automatic gates off then. Goodness knows what they think of them now!