On Friday, March 26, 2010 at 5:23:43 PM UTC, chudford wrote:
My Daughter has just bought an old house with oak beams that have been
coated in thick black paint/varnish.
Is there any way that they can be stripped back to the original wood
surface in situ without wrecking the surrounding ceiling?

Firstly, consider not stripping. The black is part and parcel of the history of the house. If she is determined to impose her stamp on the beams then there are products with gels that will strip off paint but they are particularly unpleasant to operate and you simply protect the adjacent ceiling with duct tape or the like.
I used https://www.stripperspaintremovers.com/ the one was 4-F for stone but gear up with all the safety stuff
Chris G