Doctors will be able to prescribe cannabis products to patients in the UK from today following the landmark move by the Government.
The Home Secretary announced last month that cannabis could be prescribed from November 1 for medicinal use in England, Scotland and Wales.
These products will only be prescribed on a case-by-case basis by specialist doctors - not GPs - after all other treatment options have been exhausted, the Daily Mail reports.
The dramatic change to policy followed a review into several high profile cases of patients who were denied products containing THC - the psychoactive compound in cannabis that causes a "high".
The mother of Billy Caldwell, who was given a special licence by Sajid Javid after his supply of cannabis oil was confiscated at Heathrow airport, has today spoken of her joy.
In an interview on Loose Women this morning, Ms Caldwell described the move to make medicinal cannabis products legal as being "absolutely incredible".
She said: "The Home Secretary listened, he made a promise, he kept his promise and he moved with speed, and for that he has to be applauded for."
Ms Caldwell admitted she has yet to read the guidelines, which she branded a "minefield" because of the swathes of jargon.
She fears her own son Billy, who she fought to get medicinal cannabis for, may still not come under the guidelines because she is unclear on what they mean.
Ms Caldwell told Sky News: "For me what started off as a journey which was about the needs of my little boy actually turned into something, proved to be something, a lot bigger. It proved to be the needs of a nation.
"Medicinal cannabis gave me back my right as a mummy to hope, but the most important thing medicinal cannabis has done is given Billy back his right to life."
In desperation to ensure he can get hold of the THC-containing cannabis oil that is helping him with his seizures, she is flying to Canada to stock up on Billy's supplies.
The Home Secretary has insisted today's change is not the first step towards the broader legalisation of cannabis.
While the evidence supporting medicinal cannabis builds, Mr Javid added the Government believes it is important that access to these medicines remains strictly controlled to prevent misuse.
Prescriptions will therefore only be made by doctors on the specialist register of the General Medicine Council, a statement claimed.
These medics are thought to include neurologists, who generally treat epilepsy patients, among others.
Dr Saoirse O'Sullivan, an associate professor at the University of Nottingham, told Sky News many people will likely be disappointed by the strict prescription regulations around medicinal cannabis products.
Many use the drug to combat mental-health conditions, such as depression and anxiety, which are typically managed by their GPs, who will not be able to prescribe these treatments, she added.
Clark French, of the United Patients Alliance, added specialists are going to be inundated with requests for cannabis products and hopes the law will be expanded to allow prescriptions to be made by general practitioners.
Blair Gibbs, policy head of The Centre for Medicinal Cannabis, said: "This has moved incredibly fast - leading to possibly the biggest ever overnight change in prescription medicine.
"It has been a brave decision to start with this, but as research and understanding is accrued, the decision to broaden the access and availability of cannabis-based medicines will become less difficult."
He added the CMC is putting together policy proposals for the use of medicinal cannabis in the UK, which will be published in the coming weeks.
But not everyone thinks the law change is a positive move.
Speaking on Good Morning Britain, pain medicine consultant Dr Rajesh Munglani said: 'At the moment we have this issue that we can't easily predict who is going to respond and we could easily harm four times as many people as we help.
"The latest evidence suggests you have to treat 28 people before one person gets significant relief from cannabis."
He added that of those 28 people, four would be "significantly" harmed due to the development of mental-health issues, such as psychosis.
Dr Munglani also worried doctors may become "inadvertent drug dealers".
He argued it will be difficult for medics to tell which patients are coming to them because they legitimately need pain relief and which just want access to the drug.
But Professor David Nutt, a former Government drug tsar, called the law change "a revolution", arguing any side effects are short lived.
He added the legislation will allow scientists to more easily study cannabis to better understand its benefits.
Mr Javid announced on 19 June that the Misuse of Drugs Regulations act of 2001 was being reviewed in a two-part investigation to allow for the prescription of medicinal-cannabis products.
In the first part of the review, the chief medical advisor, Professor Dame Sally Davies, concluded there was evidence that medicinal cannabis has therapeutic benefits.
The second part, carried out by the Advisory Council on the Misuse of Drugs (ACMD), recommended drugs that meet a clear definition of a cannabis-derived medicinal products should be placed in Schedule 2 of the Misuse of Drugs Regulations 2001.
Cannabis was previously considered Schedule 1. Drugs in this class are thought to have no medicinal value and therefore cannot be legally possessed or prescribed.
Schedule 2 drugs, such as ketamine, are those that can be prescribed and supplied by doctors and pharmacists. They can also be legally possessed by anyone with a prescription.
According to Mr Javid, cannabis drugs will only will be re-classed as Schedule 2 if they meet the following:
• Contain cannabis, cannabis resin, the compound cannabinol or a cannabinol derivative
•Are produced for medicinal use in humans
•Are a medicinal product or used as an ingredient in a medicinal product
Cannabidiol (CBD) oil can already legally be bought on the High Street due to it not containing the psychoactive compound THC.
"I have been clear my intention was always to ensure patients have access to the most appropriate course of medical treatment,' Mr Javid said in the statement, which was delivered by Baroness Williams of Trafford, minister of state at the Home Office in the House of Lords.
"I stressed the importance of acting swiftly to ensure that where medically appropriate, these products could be available to be prescribed to patients.
"I have been clear this should be achieved at the earliest opportunity whilst ensuring the appropriate safeguards were in place to minimise the risks of misuse and diversion."
Hannah Deacon called the law change "momentous".
Her six-year-old son Alfie has a rare form of epilepsy, which can cause him to have up to 30 seizures a day.
"Today is a momentous day for every patient and family with a suffering child who wish to access medicinal cannabis," Ms Deacon said.
"We urge the medical world to get behind these reforms so they can help the tens of thousands of people who are in urgent need of help.
"I have personally seen how my son's life has changed due to the medical cannabis he is now prescribed.
"As a family we were facing his death. Now we are facing his life, full of joy and hope, which is something I wish for each and every person in this country who could benefit from this medicine."
Mr Javid insisted, however, the re-scheduling of cannabis products will not led to the drug being legalised for recreational use.
"I have been consistently clear that I have no intention of legalising the recreational use of cannabis," he said.
"To take account of the particular risk of misuse of cannabis by smoking and the operational impacts on enforcement agencies, the 2018 Regulations continue to prohibit smoking of cannabis, including of cannabis-based products for medicinal use in humans.
"These regulations are not an end in themselves.
"The ACMD will be conducting a long-term review of cannabis and the National Institute for Health and Care Excellence (NICE) has been commissioned to provide advice for clinicians by October next year.
"The Government will monitor the impact of the policy closely as the evidence-base develops and review when the ACMD provides its final advice."
Mr Javid added his officials are working closely with the Department of Health in Northern Ireland, "which intends to mirror these legislative amendments".
Genevieve Edwards, director of external affairs at the MS Society, said: 'This is a landmark moment as the UK comes closer to joining countries around the world to offer access to cannabis for medicinal use.
"MS is often painful and exhausting, and this change in the law could have a huge impact for up to 10,000 people with the condition to relieve their pain and muscle spasms.
"It's crucial that specialist doctors can prescribe it in a fair and timely way on the NHS for everyone who could benefit, and we welcome robust guidance being put in place to help them make their decisions."