If the law passes and receives royal assent, it would still be four years before an assisted dying service was implemented.

Opponents of the Terminally Ill Adults (End of Life) Bill also believe they may have the numbers to see it off the proposed decriminalisation in England and Wales.

After much debate, the bill to legalise suicide for terminally ill adults faces its critical House of Commons vote on Friday. John Rentoul looks at what might happen