I've had a cable made up, 8mm wire, 60cm by Ocean Rigging at Lymington Yacht Haven, I called them up with the request and an hour later the cable was ready to be picked up, £32. Breaking strain is approx 3.5 tonnes, more than enough. I'm giving them a shout as I was well impressed.
It was fitted last night, after 8 or so lifts with the anchor hanging in various positions underneath it appears to work everytime, the anchor when lifted slowly (I didn't try fast) rotates to the required position as the cable bends round the roller; no hint on any catching of the anchor by the roller causing the trip to break. An extended test in real at sea conditions is required to know it's a 100% fix.
anchor lift.mp4
Notes:
I may remove the shackle between the cable and swivel later, the cable will fit into the swivel.
The shackles still needs to be moused.
The orange rope is a floater it is to allow the anchor to the retrieved shank first after tripping.
The heavy duty copper crimp edge was filed smooth to reduce chafe on the rope trip.
The cable tie round the cable near the rope trip end does nothing, I will remove it.
I'd say the cable it just long enough, it could have been made a bit longer.
The cable is attached to the bottom of the anchor shank, this is important for the anchor to rotate into position as the cable bend round the roller.
The random seeming shackel on the right will have a short rope attached to the anchor to stop the anchor falling into the water while underway (eeek!) in the event of a windlass fail.