A liquid, known as 5-ALA, uses a fluorescent dye to make cancerous cells show up under a blue light.
This enables surgeons to more precisely target brain tumour tissue during surgery to remove it, and helps to spare healthy brain cells.
Research suggests a whole tumour can be successfully removed in 70% of cases where 5-ALA is used.
This is up from about 30% without it.
The treatment has been available in some NHS hospitals but will now be available in every neurological centre in England.
Professor Ashkan was one of the first doctors in the country to use the 5-ALA treatment over a decade ago.
Since then, he has been training medics from across the world.
He told Sky News: “This drug helps us because it can differentiate and delineate a tumour a lot better than it would be under an ordinary white light, so the better we can see, the more clear the margins.
“You’re going to be able to remove more of the tumour, and hopefully with less risks, and therefore actually get a better outcome for the patients.”
Professor Ashkan says he wishes the drug could have been rolled out earlier.
He added: “This is a great advancement for patients, at the end of the day we are here to help our patients so we have got an extra tool which is now widely available, let’s use it.”
The drug costs £1,000 per person and the specialist equipment costs in excess of £30,000 each time it is put in place.
German manufacturer Medac, which makes the “pink drink”, told Sky News it would “struggle to supply” the drug to the UK market after Brexit.
It added that the price “will inevitably go up” and it will “consider increasing prices” after Britain leaves the European Union.
The rollout of the drug comes a year after the death of Baroness Tessa Jowell from brain cancer.
The Labour MP was diagnosed with a glioblastoma, the most common cancerous brain tumour in adults, in May 2017.
She went on to call for better funding and treatments for the disease, and campaigned heavily for the introduction of 5-ALA.
Jess Mills, the late MP’s daughter, now campaigns for better treatment for people diagnosed with brain cancer across the UK,
She told Sky News: “It’s a moment to feel proud with what we’re starting to achieve by delivering her legacy.
“A year on, I feel lots of things. I miss her more and more everyday if that’s possible, but I also have a huge sense of pride of what we’re achieving in her name in the way she would want it to be done which is full of optimism, forward thinking and with huge ambition.”
Ms Mills, who now looks after a charity in her mum’s name, added: “It’s a really important step but my god there’s so much to do, and that’s what mum would say, she would say this is fantastic but think of everything else we’ve got to do as well.
“And that’s how I feel because this is a really important step but there is so much work that needs to be done, not just for brain cancer patients but for all those patients who are told their cancer is untreatable at the point of diagnosis.”
Health Secretary Matt Hancock said: “I am proud to announce we have now rolled out this groundbreaking treatment aid across the country, transforming care for 2,000 patients every year – a fitting testament to Tessa’s memory.
“A cancer diagnosis is life-changing, but I want every single patient to feel reassured that they have access to the best and fastest care in our wonderful NHS.”
In response to Medac’s comments that the price of the drug will rise after Brexit, Mr Hancock said: “There’s absolutely no reason why being able to buy drugs should be any different, we’ve already got in place agreements to make sure that drugs can flow in whatever the Brexit scenario and we can buy drugs from all over the world.
“We’ve always bought drugs from outside the EU as well as inside the EU so I’m absolutely determined that will continue in the future.
“There’s many companies that want to sell the very best drugs to the NHS. The NHS drives a hard bargain to get good value for money and I’m sure we’ll do it this time too.”
Emma Greenwood, Cancer Research UK’s director of policy and public affairs, said: “Brain tumours remain a huge challenge, with survival barely improving over the last 30 years, and making 5-ALA available across the NHS is one of Dame Tessa Jowell’s many legacies.”
