All depends on the pine, in general probably wont harm it, but I doubt it will look too wonderful for a fair while with such drastic treatment

You can't pollard or coppice conifers in the same way you can with deciduous trees. If you cut the tops off they will sprout again (probably) but generally create a rather ugly specimen.
As Bluespruce says it depends on the species but in general conifers should be clipped regularly and little at a time.

Only a few pines stump-sprout at all well, and most of them won't grow in the UK--they are generally Mediterranean species. You may be able to cut it back at least a little, but chopping the top off is a guaranteed way to get a truly ugly pine, even if it doesn't kill it!