It was meant to be one of the proudest moments of her life as Sheena Rowen arrived at Canterbury Cathedral to watch her only son receive his degree.

The 62-year-old widow had travelled 200 miles from Bridport, in Dorset, to attend the graduation day – only to be turned away heartbroken at the door by University of Kent officials because she had lost her ticket.

She was left standing outside the city landmark in tears as other parents celebrated the occasion, despite showing proof she had paid for her ticket online.

It meant Mrs Rowen, who has brought up her two children alone after being widowed eight years ago, missed seeing son James, 21, receive his BSc in wildlife conservation.

She said: "I paid £40 for two tickets as my daughter was hoping to come too, but she was stuck in France.

"We emailed the university to say we had lost the tickets but never got a reply. But as I had a printout of the payment, I thought that would suffice.

"But they wouldn't accept it, even though the date of payment was clearly labelled. Neither would they give me a replacement ticket, saying that I might sell it.

"I couldn't believe my ears – this was my son's graduation that I had come all this way for.

"I have been a single mother for some years now and both of my children are at university, at great personal expense.

"It cost me more than £400 to travel and stay in a B&B in Canterbury overnight, but I did not get to see the moment. My day was ruined and I was, and still am, heartbroken."

Mrs Rowen added: "The University of Kent seem to think that they are in the game of selling tickets, rather than allowing parents to see their children pass through the gates and into the outside world.

"I cannot believe the way that I was treated by the university. They may have climbed the league tables but to me they are rock bottom."

University spokesman Gary Hughes said: "If we were to let anyone in with a home-printed proof of purchase, rather than the actual ticket, we would be in danger of exceeding our capacity as the proof of purchase could be produced in addition to the tickets, thus doubling that student's guest allocation.

"While ticket duplication is clearly not the case in this instance, and while we encourage discretion with our staff on the door, we have to ensure universality with our implementation of procedures such as this to avoid double standards."

He added: "When collecting tickets, all students are instructed that loss of the tickets could result in guests not gaining access to the ceremony, or at the very least resulting in their guests needing to wait until the end of the queue.

"This should not be seen as a punitive measure, it is simply our way of safeguarding that those in the ceremony are genuine ticket holders."