I thought they might not be serious.
I thought maybe I'd be able to turn up, take a look at the trench, take some photos then run off before the night set in.
But when I reached Shiplake College to find teachers Chris Bridgeman and Jon Cooksey in combats, wielding guns and throwing 'my' sleeping bag at me, I knew there'd be no escape.
Not, of course, that the many millions of soldiers who lived out their lives in World War One trenches had any choice either.
And the life-sized WWI trench at Shiplake is designed to give today's teenagers an idea of the conditions their counterparts had to endure nearly a hundred years ago.
|A view of the Shiplake trench|
"It's remarkably accurate," says Jon Cooksey, a military historian by trade who teaches at Shiplake two days a week.
"We studied photos of German and British trenches, then Chris built it to the exact same dimensions."
Jon is clearly in his element and, alongside Chris, soon has his troops working to a sentry duty rota, responding to rank, and making the officers (i.e. adults) tea.
He believes the trench is a fascinating social experiment, and that today's youngsters are surprisingly similar to their World War One forebears.
As an example, once the darkness encroaches on games of cards, some of the 13 and 14 year olds in the trench begin to sing.
"They just started spontaneously," says Jon. "It passes time because there's nothing else to do, it's a group activity.
"That's exactly what they would have done in a World War One trench."
|'Soldiers' play cards in the trench|
Jon's colleague Chris and the students spent six or seven weeks digging the trench, first using machinery, then - painstakingly - by hand.
"We're just hoping they'll get some idea of what trench warfare was like," says Chris.
"With the passing of grandparents and great-grandparents, a lot of that's lost and they don't really understand it.
"So bringing them into the trench to actually see, and properly take part, is important."
The evening begins quietly as the troops settle in but, just before 11pm, the trench is rattled by a series of explosions.
The boys immediately reach for their guns, although some naively try to aim at the smoke above them, rather than facing out of the trench at the enemy in the darkness.
It turns out that enemy is the headteacher, equipped with a box of fireworks. Happily, all survive the bombardment, although the head admits to having grave fears should a school inspection team turn up.
|Negotiating the water in the morning|
Back in the trench the soldiers eventually settle down at gone 1am, as the sentries change for the third time.
But soon the rain starts to come down - and it's this that made trench life truly unbearable in the great wars of the last century.
By 4am, the trench is awash in a foot and a half of water, and ladders designed to go 'over the top' are employed practically as rafts. After all, no one wants to develop trench foot in Shiplake, of all places.
5am rolls in and the bedraggled, damp Year 9s are beating a hasty retreat to the school, a shower, some warmth and some clean clothes.
It looks unlikely they'll be back for a second consecutive night, let alone months of campaigning on the Continent.