If the tree is vital, you can prune it severely and it will bounce back without a hitch. However, the best time to prune is during the Summer.

Josh

Even if you cut it back to ground level it'd still grow back, but with multiple stems. So you have a lot of leeway for sizing and shaping it the way you want.

What Josh said. How much stored energy the tree has and how robustly it's growing largely determines how well the tree will respond. I wouldn't risk cutting back a Ficus benjamina, lyrata, or elastica really hard in the UK (like back to the ground or completely defoliating ...... or for that matter - ALMOST completely defoliating it). They just don't respond in northern latitudes like they do in more southerly climes. Still, you can usually substantially reduce a tree if you know how to prune it back so there is an eye appealing structure to build on.

Summer is definitely the best time for you - like in mid-Jun - mid-Jul.

Al

Thanks all for your advice, that's much appreciated. I move in a couple of weeks, so I don't have the option of waiting til the summer, but I can proceed with a bit more confidence. Thanks.

David1956, I hope you post pictures of your ficus pre- and post-move. We'd love to see it and how you decided to take care of it. Please?
Pat

Remember when you prune it will leak masses of white latex so surround it with newspaper etc on the floor. Also when you move, it will probably lose the rest of its leaves in protest. Once you get it installed in the new house just leave it alone to recuperate (do not overwater) and in a few weeks you should see new leaves starting. I have done this.

If Ficus pruning cuts ooze latex, spray the cuts with a spritzer filled with tap water - they'll stop oozing almost immediately. The plant won't lose foliage unless you ,move it from a bright to a dim spot, or you site it in an exposure MUCH brighter than it was previously conditioned to.

Al

I had an 18ft ficus. I cut it 2/3 down in winter (had construction going on in the house and had no choice), moved it to a small room.

It exploded in Spring. Never missed a beat. Don't worry about it!

You'll shape it in Spring, just cut it.

Jane

Thanks everyone for your helpful advice. I've posted a picture of the beast as it stands right now and, as you can see, it has lost its leaves completely at the lower levels, so I hope to cut it back to no more than a foot above soil level.

David