Ok Manual VR4
Stock Clutch not that old at all maybe 6-10000 miles
When cold you can launch the car and it goes great and leaps away. loading it up in high gear no problem.
However. Cruise on the motorway for an hour and get everything hot, then pulling out in 5th gear and it slips.
Are the casings expanding?
The clutch slave has been off the car and emptied, checked it is free and total fluid replacement and bleed.
The clutch pedal has been off the car and investigated and tweaked in case it was holding residual pressure on the master.
Is something dropping on the clutch? water oil? No signs of any leaks or drips.
Can oil from the main seal find it's way onto the friction surface?
But then next time you start it it is great and grips well.
Highly confusing.