As I walked along the upper floor of C-wing at Shrewsbury Prison, I suddenly got a whiff of a foul odour. It smelt like someone who had not washed their clothes for months, of dirty skin and hair. It was dreadful and I turned up my nose.

"Smell that?!" I asked my friend Paul as we stood outside one of the cells. He did. I stepped inside but the smell was gone and I didn't really think about it again. Well, that is until we were led on a group tour through the prison ahead of 'lights out'.

We were sleeping over at the old Victorian slammer and by the time midnight rolled around, they were shutting off all the lights and we would be permitted to explore in blackness. But for now, we were learning of the history of this fascinating place, the reasons people would be locked up, the awful conditions in which they were kept and then, because it's important to the story, the reports of paranormal activity.

Read more: Genuinely scary Halloween events in and around Birmingham that you should never take little kids to

Poll: Have you started your Christmas shopping yet?

C-wing was known for hauntings, we were told. Our guide, dressed like a screw, didn't over-egg the spooky stories like they do on ghost walks. He let the facts, which are sinister enough on their own, do all the scaring. I learnt loads.

He did tell us how he once saw a ball roll, by itself, across the floor. The ghost of a playful eight-year-old boy has driven staff away from working here, and it might well have been him. A grey lady has been spotted haunting it too, though our guard had no first hand run-ins. I hoped I wouldn't either.

He also explained that there's a force of some kind, the malevolent spirit of a man who grabs the ankles of women who walk by his cell, sometimes pushing them against the wall. He didn't need to say which cell, I knew already from that particularly horrendous smell. When he pointed to the exact place I'd smelt it, the dread really started to sink in.

I'm quite a brave guy, I think. I've taken on scare mazes at Alton Towers, ridden the ghost train at Drayton Manor. I've taken the ghost walk at Aston Hall and even spotted a sinister character peering through its upper windows. More recently, I've faced the frenetic madness of the Luna Springs scare maze. I never lost sleep over any of them.

And yet this place brought about feelings that made those ones pale in comparison. Those all felt deliberate, frightening by design. Shrewsbury Prison is just unsettling on a deep level, right down to its Georgian tunnels and foundations; human history is more frightening than the tales of ghoulies and ghosts.

Surely things couldn't get any more blood-curdling than C-wing?! Wrong. As we turned a corner upstairs to circle back to A-wing where we were sleeping for the night, we passed yet more spine-chilling spots.

One was the chamber where the hangmen of the past spent the night before an execution, a headless mannequin that I wasn't looking forward to seeing in the dark. The second was the execution chamber itself, complete with a noose and a room where another unsettling dummy showed exactly where the condemned man would be held before he took that long drop down to nowhere.

I hated reading the stories of those who were hanged in Shrewsbury, most recently in 1961. So recently, I shuddered. If there's going to be any bad, negative energy trapped anywhere, it'd be here. And yet, the room with its viewing chairs felt surprisingly warm compared to the rest of the prison.

Another room told the stories of famous British killers of history, from Amelia Dyer and her baby farm up to Fred and Rose West. I didn't spend much time in there, not because it makes me nervous but because I can't be bothered to give the killers much thought at all.

The winding route continued, through passageways, beside the hospital wing, a double-wide cell used for treating prisoners in palliative care and then, I realised with yet more sinking feelings, my own cell for the night.

On A-wing there are more than 100 cells with non-working toilets, sinks, basic bunk beds and not much else besides. This was a working prison right up until 2013 and I read the graffiti from former inmates, some counting down days until release, others writing strange messages in anagrams or code that I couldn't decipher.

I'd popped down to the prison canteen for a burger and chips (where they serve cockle-warming alcohol, if you need the extra fortitude) and roamed the gift shop, which was the old morgue, before making my way back upstairs in time for lights out.

Things changed for the worse once the lights were off (or for the better for the thrill-seekers who ran around playing hide and seek). My friend Paul was staying in the cell next door so we decided to go roaming with our head torches; the sleepover was fully booked and yet there's so much space to free roam that most of the time, you're by yourself in the prison's nooks and corridors.

On the very upper floor of A-block we felt the chill and sensed an inexplicable feeling of unhappiness. Walking past the open cells, yawning dark holes like the many black eyes of some giant spider, was scary as hell. You never knew what was in there, looking back.

Some ghost hunting visitors were holding some kind of séance round in the hanging chamber and I had no intention of messing around with that, so we visited C-block instead. A door slammed, seemingly on its own, and I ran through the night at a speed I don't think I've ever physically managed before. I was glad when it turned out to be another visitor, playing silly beggars.

Back outside our cells, Paul and I debriefed on the experience in the dark. We both agreed that the more time we'd spent exploring, the less scared we were feeling. My hat pinged off the top of my head on its own. Apparently, I was getting too cocky.

We retired to our cells, mine full of snacks and treats I'd brought along for midnight feel-better fuel. It was like I was the prison commissary shop, with tuck of every kind, and yet I didn't have the appetite to eat any of it.

We'd been warned to bring air beds because the prison mattresses are notoriously uncomfortable. I had all my home comforts, my pillow and duvet, but I couldn't rest. I couldn't face turning my room light out, so I lay down and listened to footsteps in the night, the drips of water outside, and looked at the bunk above me imagining how horrible it'd be to have a criminal up there, snoring. I counted down the minutes until morning.

If I ever thought about committing crimes before, I never would again after spending the night in Shrewsbury. I'll come back here for sure, but in the light of day for another tour, but you'll never catch me sleeping in a slammer again.

These sleepovers are slowing up for winter, because it's cold in the old cells at the best of times, but they are doing ghostly night tours by torchlight if you're feeling brave. Most Haunted are there for a sleepover in November if you fancy taking part in some paranormal research - tickets to that are here.

Best of luck! Hopefully you won't need it...