MACHINE guns rattle overhead and shells explode with a bang as we walk through the First World War trenches.

As our eyes become accustomed to the smoke and dark, we spot the maimed and dying soldiers, desperate for medical attention.

Rushing to their aid are uniformed nurses. So far, it’s like walking on to the set of Downton Abbey – until we notice that, underneath their starched caps, these angels of mercy have hideously deformed faces and very sharp teeth.

And these savage creatures are reaching out to grab us with their gnarled hands.

Welcome to the incredibly realistic and terrifying world of Halloween Horror Nights at Florida’s Universal Studios.

Nightingales is one of eight haunted houses that spring up at this time of year in the Orlando theme park. It certainly brings a whole new meaning to the horror of the Somme.

Halloween is a big deal Stateside, and this is the biggest macabre event in America. More than 1,000 actors, in frightfully grim costumes, are used to bring the nightmarish scenes to life.

It takes 12 months to prepare these spectacular experiences. Great attention to detail means that the houses could even be used as film sets. In fact, The Thing, new this year, uses props from the forthcoming Universal horror film of the same name.

It’s a prequel to the 1982 cult classic, in which we see how ‘the thing’ took over an Antarctic research station.

Going into sub-zero temperatures is chilling – in more ways than one when the creatures start appearing – but is actually a relief from the hot Florida night.

Also spookily cold is Winter’s Night, where snow falls on a gothic cemetery, ghosts rise from their graves and creepy statues come alive and jump out at you.

Before we set off to experience the horror, we’re given survival tips, such as: “Just keep telling yourself ‘It’s only a nightmare, it’s only a nightmare’.”

I am also relieved to discover that the actors aren’t allowed to touch you – not that that’s much consolation when they leap in front of you or snarl in your face.