Today’s vote is hugely significant. It now looks highly likely that assisted dying will be introduced in England and Wales.

The vote by MPs to approve Kim Leadbeater’s bill is arguably the biggest vote regarding bodily autonomy since the legalisation of abortion in Great Britain in 1967.

In the baking heat of London’s Parliament Square today, hundreds of campaigners stood chanting their views – both for and against assisted dying – amid a sea of colourful banners and placards.

There was emotion too. Some carried photos of loved ones who died in pain, while others expressed their fears for the vulnerable in society.

The debate around assisted dying has been a polarised one – and there are still hurdles to cross before it will be a reality here.

The Terminally Ill (End of Life) Bill will now go to the Lords, where it is likely to spend several months undergoing the same line-by-line scrutiny that it did before MPs.

Later this year, perhaps around October, the bill would come back to the Commons for any changes to be voted on and it could then be sent for Royal Assent.

So when could assisted dying become available in England and Wales?

The government has said it could take up to four years to set up an assisted dying service, meaning it could be 2029 or even 2030 before the first medically-assisted death happens.

Health minister Stephen Kinnock said this delay was needed to ensure “safe and effective implementation” of an “entirely new service with robust safeguards and protections” which would need to be “carefully developed and tested”.

Under the proposals, mentally competent, terminally ill adults in England and Wales with a life expectancy of less than six months would be eligible for an assisted death.

They would need to make two separate declarations, signed and witnessed, about their “clear, settled and informed” wish to die, and satisfy two independent doctors that they are eligible, and have not been coerced.

There would be at least a seven-day gap between each assessment.

The application would then go before a multidisciplinary panel comprising a psychiatrist, social worker and a lawyer.

The panel would hear evidence from at least one of the doctors and the applicant, possibly via live video.

If the panel approved the application there would be a further 14-day “period of reflection” which could be cut to 48 hours if the patient is likely to die within a month.

Ms Leadbeater has said the whole process could take up to two months, which does raise the risk of people dying while they are waiting for approval.

The process is also far longer than other comparable services on which the Leadbeater bill is based.

In Oregon, the first US state to legalise assisted dying nearly 30 years ago, there is a 15-day waiting period between the first and second request. Since 2020, this restriction has been lifted for patients at risk of imminent death.

In California, the 15-day cooling off period has been cut to 48 hours because of the risk of patients dying before their medically assisted death is approved.

England’s chief medical officer for England Professor Chris Whitty has cautioned against creating a system that would risk terminally ill patients being “stuck in a bureaucratic thicket” in their final months of life.

While the Leadbeater bill contains a lot of detail, there is still plenty to sort out if it becomes law.

If the legislation is passed, the Health Secretary Wes Streeting, who voted against the bill, will be required to set up an assisted dying service under the NHS

This means sorting out the training for doctors who will assess patients for capacity and for any signs of coercion or pressure, plus creating safeguards for those with a learning disability.

When MPs first voted on the issue in November, the plans included a High Court judge who would need to approve each case.

That proposal has now been dropped and replaced with the panel.

The new service will be overseen by a voluntary assisted dying commissioner, who will be either a serving or retired senior judge.

Their role will include appointing members of review panels, referring cases to them and monitoring the operation of the law.

Although the proposed law is based on legislation in 10 US states and Australia, there are important differences.

In California, patients are able to store the lethal medication at home and they are not required to have a medical professional present when they die.

Under the Leadbeater bill, a doctor would prepare the drug, and be present when the patient self-administers it.

This would usually mean swallowing the lethal substance, although if that is not possible, the bill allows for a “medical device” to be used to enable the patient to ingest it.

There will be strict limits on what a doctor can and can’t do. Mr Kinnock said it would be legal for them to help a patient sit up and make them comfortable, but not for them to tip a cup of pills into their mouth.

The health secretary will regulate what drugs can be used. In all likelihood these will come in a powdered form and need to be mixed with liquid for swallowing.

I was present at an assisted death in California and witnessed the doctor adding fruit juice to the drug in order to make it more palatable and less bitter for the patient to swallow.

On that occasion the patient, Wayne Hawkins, was unconscious within a few minutes of swallowing the drug and died in around 35 minutes.

Deaths usually occur within an hour although there have been rare cases of it taking several days.

In some other countries that have legalised assisted dying, euthanasia is permitted, whereby a doctor or nurse administers the lethal dose, usually by injection.

Euthanasia is allowed in the Netherlands, Belgium, Spain, Canada, Australia and New Zealand, but even for most supporters of assisted dying here, it is seen as a step too far.

An impact assessment, carried out by civil servants estimated there could be between 1,042 and 4,559 assisted deaths in the 10th year after the law came into force.

That upper estimate would represent around 1% of all deaths in England and Wales.

Whatever happens to the Leadbeater bill in the coming months, assisted dying is coming to the British Isles.

The Isle of Man has already approved an assisted dying bill and Jersey is also committed to changing the law.

A bill to legalise assisted dying in Scotland has passed an initial vote at Holyrood, but faces further hurdles. The Scottish bill does not have a life expectancy timescale for eligibility and instead refers to advanced and progressive disease that is expected to cause premature death.

Assisted dying, or assisted suicide as many critics prefer to call it, remains illegal in most of the world.

Modern medicine means that healthcare systems can keep people alive longer than ever before, but often with limited quality of life.

Supporters say that assisted dying gives autonomy and control to patients. For opponents it is a chilling and dangerous step which puts the vulnerable at risk of coercion.

Whatever happens to the bill at Westminster, this heated and polarising debate will continue.