I learnt something new the other day:D. The trailer I picked up was quite an old beast. It had a cable break on it. I put the break on (there was a wall of old tyres behind it) and tried to pick it up. The whole thing moved backward with the break on. When I asked a fitter why it was happening he said the cables tend to sag with time so they don’t allways work properly - that was that defcted. When I pick one up in future put the red airline on for five or six seconds, then take it off and this locks the trailer service breaks on. Picked it up dead easy without chasing it all round the airfield. Just thought I’d pass it on 
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Yup, cable parking brakes can be a right pain 
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You need the arms of a Gorilla to get the brakes to hold the trailer. When it comes to knocking them off your best bet is to to hold the handle in the release position, put your boot on the slack bit of cable in front of you and unroll some more cable off the drum.
The cable drum spindle usually needs to be greased, because the grease-monkeys often forget, what with the pressure they are under to get the trailer serviced n back out, combined with the frequency they get cable braked trailers (ie. almost never).
That trick with the red line works for any trailer, some of the older trailers loose their air so that the parking brake releases and you can get a 
when you try to hook-up.
The day when you don’t learn anything is the day when you need to give up driving. Some days you only relearn something you forgot, often quite forcefully 
, but if you go several days, its because your getting complacent. Thats a dangerous attitude in this game. 
I try not to get complacent because the first and only time I did; it BIT ME IN THE BUM .