On my last night in Essen I had a small Incident. (Nobody hurt.)
I usually sublet a parking space from the people I demonstrate
for, but I have to get the car out by the end of Sunday and put it
somewhere else before I set off for home on Monday morning. My usual
hotel doesn't have parking space, so I have found a couple of street
locations nearby that work.
In this case I was backing in next to another car, but hadn't realised
that there was a sloping concrete pedestrian overpass immediately
behind: the bottom of it was about a metre and a half off the ground,
so didn't show up in rear lights or on the parking sensor. I was going
in slowly of course, and heard a gentle tap… followed by a
comprehensive cracking as the back window crazed around a small hole
(which gradually became larger).
I already had much of my luggage in the boot, with the cover closed,
so the best bet seemed to be to leave it there. Thanks to help from a
local with whom I'd been working, I found a covered car park for the
night within walking range of the hotel, and backed up against the
wall. (So a potential thief would have had to notice the problem,
decide to search the car, then get in round the sharp cracked glass
without being able to open the tailgate. Nobody did.)
The next step was to get home. I tried the local Halfords-equivalent
(ATU), but it seems nobody sells emergency plastic screens any more,
and while they did connect me with a glass repair place they couldn't
do anything that day. So I went to a local supermarket and bought
clingfilm and parcel tape, and rigged up an emergency cover.

It worked remarkably well. I'd expected to have to restrict my speed
to well below the limits, but in fact there was very little suction
and I took it up to 130km/h with no problem; what was most notable was
that every time I overtook a lorry, or was overtaken by one, there was
a great wave of turbulence and flapping, which was what did most of
the damage. (And a very occasional rear window wipe caused by the
car's systems, e.g. if I had forgotten to turn off the front wipers
before engaging reverse gear; I could have left the rear wiper raised,
but that would have put it out in the slipstream as I went along.) The
Channel Tunnel people raised no objection at all (I suspect they were
too bored to notice), and I got home on Monday night as planned,
having done all the usual shopping en route (German beer, Belgian pipe
tobacco, French wine boxes and cheese).
I did repairs along the way. If this happens again, I'll probably try
to buy clear tape, apply it in overlapping strips and omit the
clingfilm completely.
The simplest way to get the glass replaced turned out to be via my
insurance company, and I sorted that out on Tuesday morning.
They had the offer of my turning up in Slough on the next Thursday, or
waiting until Monday for one of their mobile units. I could have gone
to Slough, but my feeling was that the emergency rig had done its job
well in an emergency and shouldn't be asked to do more. (Also, I
didn't need the car for the intervening time.)

A bit of expense, no lasting damage, and a reminder to know the
terrain better; just because it looks clear doesn't mean it is.