I’m posting this here as the clutch on my Series 3 Lightweight operates in same way as a later Defender. There’s a master cylinder then a metal pipe leading down to slave cylinder mounted on gearbox bellhousing.

Before the beginning of the lockdown I drove it into town and lost all the gears at traffic lights. The clutch went straight to the floor with no resistance. After much tooting from the cars behind me and fiddling with the 4 wheel drive & low / high ratio I suddenly got a clutch pedal again and got home without any issues. Suspecting the slave cylinder was leaking I replaced it with a TWR one. All well & good.....until it happened again. I took the slave cylinder out & it but couldn’t see anything wrong but whilst I was puzzling with my head under the bonnet the fluid level in the master cylinder suddenly went up! Ha ha. Master cylinder! I replaced this with a genuine Girling one and had loads of issues bleeding the clutch until I finally got it working, took it for a test drive and all was well.

In the intervening time it’s not moved far - just up & down the drive. This morning I drove it about 10 miles to drop some stuff off for an elderly friend whose in isolation. No problem. Got home, did some Jones then went to go out in it again. No clutch! Checking the fluid level it’s down about 2 cm from top level but I can’t see any leaks from either the master or slave cylinder.

I’m at a loss but thinking perhaps the slave cylinder piston is not returning which may suggest a clutch problem. Anyone got any ideas?

it could be the flex hose collapsing internally. will let fluid pass when forced but not let it return quickly, but will gradually let it return.

Never thought of that one. Anyway of checking? Currently still got no clutch. Another new slave cylinder on order incase other one faulty but beginning to suspect the pushrods punched through the clutch release fork

It won't be the fork - it's the strongest bit of the car.

I can't really think of a way to test the hose that's easier than just buying a new one and fitting it. Same part as on a normal SIII btw.

Replace the hose. You will have all new so can rule it out. Does your pedal have a spring on it?

Thanks everyone for your help. Taken the master cylinder, flexible, metal pipes & slave cylinder out. Ordered longer new 5/16 UNC set screws for Slave cylinder only to find out I needed UNF so looks as if parts list wrong. Flexible seems fine but replacing anyway. Slave cylinder jammed solid in bore and couldn’t get it out! Luckily have a spare. Big problem I found was that the valve stem in master cylinder had come adrift from the spring & piston. Only discovered this whilst trying to prime it on bench. After pushing piston In it took 5 minutes to slowly return. This is a brand new Lucas Girling part & I have no idea how it has happened as I didn’t take it apart before fitting! With the correct bolts on order I’ll hopefully be back behind the wheel soon.