R56 Odd clutch behaviour

[ChasW]

I have not used my petrol 1.4 Mini for 5-6 weeks other than starting the engine once or twice. Went to drive it yesterday and when engaging reverse the clutch felt normal until I got to biting point when there was no "feeling" at all. The car started to move but when revved much above tickover the clutch started slipping. The same in forward gears. I can drive off but only very gently the slipping occurs if I go above c1800rpm.

Would appreciate any thoughts on what the cause might be?