No I'm not having a laugh, I was taking a cue from idd15's post quoted above. This post hasn't been contradicted.
If, as you infer, the power supply can be a fused spur off the ring main then I don't see an issue.
And it won't be necessary to dig a 70ft trench, an armoured cable down to the garage would be all that's needed. There is already a fused spur (actually with a circuit breaker) to power the water feature that has worked quite satisfactorily for the last 20 years, another for charging an EV shouldn't be a problem. Assuming, of course, that this is a viable solution, I'm not an electrician.