My elderly mother has deteriorated to be entirely dependent on carers and bed-bound, I wish we could be merciful and let her die but UK law (apparently) require

My elderly mother has deteriorated to be entirely dependent on carers and bed-bound, I wish we could be merciful and let her die but UK law (apparently) requires she either be starved to death - which the medics have told us is a painful, horrible death - or be kept alive, with every intervention below surgery. It's vile. She let go, they installed a feeding tube and ensured she couldn't die with what little dignity remained at the time. She came back, in body, but rapidly lost what little of her self that remained. But now she lies in bed her life forcibly extended each day; completely devoid of a life, and hopefully devoid of cognition. Frankly, it is inhumane.