Striding through the frosty court, sporting tails and a smart bowler hat, Paul Cash looks every inch the archetypal college porter. But, as he is about to demonstrate, Paul is anything but typical: dubbed "the painting porter", the 42-year-old is an acclaimed artist - whose work hangs on hallowed walls.

Leading the way through Selwyn, and into an impressive college building, Paul points out a framed canvas: a stunning snow scene, it is one of his earliest works. "I love my day job and I love my painting," he says, with a broad grin. "I'm one of those nauseatingly happy people. Sometimes I find myself laughing for no reason!"

"I hadn't painted for 20 years. And, to be honest, I didn't think I would be able to do it. But once I started, that was it - last Sunday I did two paintings in one day!"

Passionate about painting as a child, Paul remembers loving both Dali and Picasso. But, after a brief trip to art college ("I think they called me 'too much of a free radical'," he laughs), Paul put down his brushes - and took up a saw. "I became a carpenter," he explains. "That was my way of being creative."

Paul loved working with wood. But, five years ago, he suddenly lost all the strength in his left arm. "I literally couldn't lift it," he explains. "Even now, if I hold the slightest thing - even the TV remote - in my hand, I struggle to lift it." That's when Paul was diagnosed with multifocal motor neuropathy (MMN), a degenerative nervous disorder so rare it affects only a handful of patients across the UK. Among the key symptoms is asymmetric weakness in the arms, hence Paul's problems with his left bicep and his right hand.

"If you joined them both together then I'd have one really good arm," he jokes, with a wry smile. "Not being able to lift a hammer meant I couldn't be a carpenter any more. That's why I applied for the job as a porter. I loved it straight away, it's very sociable. But I still needed a new outlet for my creativity - which is why I decided to take up painting."

Starting out with acrylics, Paul admits it was painstaking work. But, after switching to oils, he realised he'd found his niche. "They take time to dry which is great," he explains. "That means I can go back and correct things, if I need to."

Citing his teenage daughter Zoe as a muse, Paul says Selwyn itself has also been a great source of inspiration. "It's such a beautiful place that just being here made me want to paint," he explains. "In fact, my first two paintings were both of Selwyn." The college went on to purchase the second picture - the aforementioned snow scene.

Now dedicating most of his spare time to painting, Paul spent his entire two-week summer holiday holed up in his home studio. "I can be quite a recluse," he laughs. "That's why I enjoy having such a sociable job."