Help! Type 4 engine loss of power

Evening people,

I was just working on my van calibrating my dash after maket not the point, just did a 5 mile round trip first half fine then when I came to drive home i had no power it was topping out about 30 to 40, but the revs were still going up but my speed stayed the same

 

If your revs are climbing but your speed isn't, I'd suspect a slipping clutch