
Warning: This article contains discussion of cancer which some readers may find distressing.
Cal Petrie thought he was 'getting old' and had a hangover when he started getting headaches after drinking just one beer.
The 23-year-old first noticed it over Christmas and thought it was just part of the aging process that he was getting a headache three or four hours after drinking, he'd take an ibuprofen and then feel alright again.
But in January this year he discovered what the actual cause of the headaches was when he was diagnosed with grade four pineoblastoma - a rare cancer in the form of a brain tumour.
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Since then he's had two operations to remove the tumour and excess fluid from his brain, as well as weeks of proton beam therapy to target the tumour with precision.

He's now in chemotherapy and the Clapham Junction man is hoping to raise awareness for the dangers of brain tumours after his 'devastating' diagnosis turned his 'whole world upside down'.
"I started to ask myself, ‘why me?’ and ‘why now?’," Cal said of the moment he got his diagnosis.
"I felt angry with the situation because it just felt so unfair although, in my head, I knew there was no-one to be angry with. I was just really unlucky.
“There are very few answers but Government funding for brain tumours is still so low.
"Everybody facing a diagnosis wants to know why these things are happening. More funding will help answer those questions and will lead to more treatment options and improved outcomes.”

He explained that doctors told him he was 'such a rare care' that they'd got quite interested in him, with Cal saying he had 'dozens of clinicians' attempting to work out why it happened to him in the hopes of preventing it from occurring again.
At the moment they're not sure whether his brain tumour developed very quickly or if it had been with him for a long time and stayed dormant until he got headaches.
Most people diagnosed with pineoblastomas are younger than 20, and symptoms can include a feeling of pressure in the skull, nausea, abnormal eye movements and the headaches that Cal got.

This weekend (13 September) his mum Lucy is doing a bike ride from London to Brighton to raise money for Brain Tumour Research, which can be donated to here.
Dr Karen Noble said: "Cal’s story reflects the devastating reality faced by so many families across the UK.
"We are campaigning to increase the national investment in research into brain tumours to at least £45 million a year.
"We need sustained investment if we are to develop kinder, more effective treatments and give brain tumour patients the best possible chance."