Cutting back a box hedge?

[Ouch77]

I have a large, mature box (with a bit of privet mixed in) hedge in my front garden (about 4-5ft heigh). It's size is such that it is affecting visibility for any vehicles on my drive.



I'd like to cut it back substantially, to remedy the visibility issue, and to reclaim some lawn space. Is this possible with Box? How far back can I trim it?

 

[lostinthelight]

This was on the RHS website: Old, neglected plants usually respond well to hard pruning in late spring (May) and can be cut back to within 15-30cm (6in-1ft) of the ground.

https://www.rhs.org.uk/advice/profile?PID=88
litl

 

[Ouch77]

Interesting reading - many thanks!