Using a breadknife or similar, insert it vertically between the pot and the soil and work all the way round the outside, to separate the soil and probably roots from the walls of the pot. Usually needs to be done a couple of times. Ensure its absolutely sopping wet, then you need two people - one to try levering it out from the top with a hand fork and pushing the pot away (or even a large garden fork shoved into the middle if that doesn't work) the other to hang on to the pot, pulling it away from the other person and pushing up through the bottom hole at the same time.

If its rootbound, its entirely possible its rooted a little bit into the walls of the pot, which can happen with pottery containers.

Gosh, thanks Bamboo. I've got a rather lethal serrated edged branch saw which would be ideal. I shall tell my friend and pass on her thanks to you in advance.

My family never knew, but I've always used the breadknife!

My dad had a favourite penknife which he used to scrape the soil from his garden tools and also pare apples! I don't think he ever washed it. He lived to a ripe old age.

then follow th ebreadknife technique but also push through the drainage holes with the handle of a wooden spoon too. I find that helps too.

Ha ha, so that's a breadknife and a wooden spoon, plus I use an old ladle from the kitchen to take Growmore out of the tub, and my old fridge racks between bricks to let plants drain properly, amazing how useful kitchen kit is outdoors...

yes they also end up in the garage, cake icing syringe for grease! really OH is the limit. I don't use his tools ;o)

Tell him you're going to use it to ice his birthday cake...!

I don't think he'd notice it as I suspect 'nil by mouth' isn't a premise of his existence.! bless him