The handbrake on my Mk3 Mondy was getting progressively worse at holding the car. The pull on the cable got gradually slacker. It failed its MOT in December for the reasons below:

Offside Rear parking brake recording little or no effect [3.7.A.7a]

Parking brake efficiency below requirements [3.7.A.10]

The test result was RBT Park Brake efficiency 14%. The garage replaced both brake cables and the handbrake worked like new. But within a fortnight or so I noticed the pulling get slacker, and its effectiveness has now waned to the extent it struggles to hold the car on any but the most level surface.

I know its difficult for people to advise, but what's the likely cause? I'm pretty hard on pulling the handbrake on, but I don't think that should result in a near total failure. Shoddy workmanship? Poor part?

Sounds like it is not auto adjusting, try applying the foot brake and then the handbrake that should make it adjust, also you shouldnt need to pull a hand brake on really hard a couple of clicks should do it, you may well have stretched the new cables

I was taught to press the handbrake button in before applying to save the ratchet and apparently it's better to guage cable tension so you don't strain the cable.

I was taught to press the handbrake button in before applying to save the ratchet and apparently it's better to guage cable tension so you don't strain the cable.

So was I, but thought it was best to relate to clicks in this instance

dont know if you got your problem sorted but the older mk3 mondeos had the big spring type auto tensioner at the lever, simply put alot of them didnt work even after the millions of recalls and the second recall for the same thing given them a new lever with a tighter spring and even after the calaper recalls for the cable brackets, the only cure for an older mk3 that will not adjust was to get a newer mk 3 lever with the manul screw adjust and fit that along with 2 new cables (after market are all good cables) set of pads. if your mondeo has the screw adjuster under the car then change the cables as they are common to seize up and new pads. if all done at once you wont belive the differnce. i worked in a ford dealer when all the recalls were done and swear 3 recalls for the same problem and on some of them that were that bad fomoco even forked out for the second revised lever with the screw adjuster.