When Derek Acorah was a boy, living with his grandmother in her Liverpool terrace, he often wondered about the steady stream of visitors through her front door.

“There always seemed to be someone calling round,” he says. “Three or four people would be ushered quietly into the parlour. What I didn’t know until later was that they were coming for readings.”

Derek’s grandmother was a psychic and when, as a child of six, he claimed to have been visited by the spirit of his dead grandfather, she declared: “Our Derek has the gift.”

“I didn’t even know my grandfather, he died before I was born,” says Derek. “He was a seafarer and died in the Indian Ocean. But when he came to me he looked real, I could feel him touching my head. It frightened me out of my skin. I later pointed him out in an old photograph, and that’s when my gran knew I had her gift.”

It wasn’t a gift he initially welcomed. “I remember saying to my mum, ‘I don’t want to talk to dead people’, but my gran took me under her wing and reassured me.”

Today Derek, 60, is the UK’s best-known spirit medium. He achieved both a cult and mainstream following as resident medium for Living TV’s popular Most Haunted which saw him investigating haunted properties, including Bradford’s Bolling Hall.

Derek’s Living TV specials included a live Halloween show, watched by more than 1.4 million viewers. He went on to star on Living TV’s Derek Acorah’s Ghost Towns and The Antiques Ghost Show, produced best-selling books and last year held a much-hyped televised seance, claiming to contact the spirit of Michael Jackson.

Derek has had his share of criticism from sceptics, but it doesn’t appear to faze him.

“They don’t bother me. Everyone is entitled to an opinion. The world is made up of many ways of thinking,” he says. “I get sackloads of letters from people I’ve helped.”

Whatever you feel about mediums, there’s no denying the comfort they bring to many bereaved people.

Audiences at Derek’s previous Bradford shows have seen how his uncannily-accurate messages can bring people a sense of peace.

“That’s what keeps mediums going,” says Derek. “By connecting with the spirit world, we bring about healing. Sudden death in particular often means unfinished business, and people need closure before they can move on. When people come to the live shows they see it’s for real.”

So how does a medium prepare for a sell-out gig? “I get there early, about 6pm. I sit quietly alone and ‘close down’,” says Derek. “I get called ten minutes before I’m due on, and by then I’m open to the spirit world. I get nerves, of course; nothing is scripted and no two shows are the same.”

Derek says he picks up sounds then visualises a spirit. Does he expect to be visited by spirits from St George’s Hall’s past?

“Spirits attached to buildings do show themselves,” says Derek. “Occasionally someone from a theatre tells me a person I mentioned worked there years ago.”

One of Derek’s strangest experiences was on board a cruise-liner. “I was on holiday with my wife. It was two days in and we were sunbathing,” he says.

“It was peaceful and calm. I drifted off to sleep and suddenly felt a coolness over me. A Scottish man was standing by me. Gwen wasn’t seeing him, so I knew it was a spirit. He had recently died and wanted to tell his wife, who was on board, that everything was okay.

“There were 2,000 people on that ship, but he guided me to her and, once I’d explained, she cried then laughed. She was overjoyed. We still get Christmas cards and letters from her.”

Some mediums see ‘the gift’ as a curse, but Derek refuses to let it rule his life. “It’s a responsibility, but you have to consider those closest to you. You learn the discipline of controlling it so it doesn’t control you. I’d go mad if I was letting spirits in all the time.”

Reading about Derek’s beliefs on his website is pretty mind-boggling, but I was struck by his faith in reincarnation.

He believes that in the afterlife we choose whether or not to return to a physical life, and whether we want a relatively easy life, or a more challenging existence.

“The ultimate aim for any spirit is to ascend. The harsher your life, the higher you ascend on the spiritual ladder,” he says. “I work all over the world and those beliefs are shared by many cultures.”

Like many mediums, especially successful television ones, Derek has warmth and charisma. I enjoy our chat and find it all quite fascinating, but I remain essentially a sceptic, albeit an open-minded one.

Derek Acorah is at St George’s Hall on Thursday, May 13. For tickets, ring (01274) 432000.