At a glance the fields of Varlet Farm, set amidst the flat Belgian countryside, look completely unremarkable. There are potatoes here, a crop of celeriac there. A tractor stands waiting to start its day’s work.

But what a day’s work! Every time he ploughs these fields farmer Dirk Cardoen knows that he might unearth bombs, shells and grenades. He has a tin tank full of them on the track to the main road, a constant reminder of his deadly additional crop.

Dirk shows us his latest finds and pulls out a couple of rusting shells. “This one’s still live,” he says, pointing at one with a wry smile.

“Don’t worry. They don’t go off very often.”

Round these parts this is known as the iron harvest, for 100 years ago this land was a First World War battlefield. Just a few kilometres from Passchendaele, Varlet Farm was under constant bombardment as the occupying Germans battled to keep it out of allied hands.

Dirk tells me that so far this year he’s found 13 shells. Last year it was 17 and in 2007 “our best year” they dug up nearly 70.

The potentially deadly finds are constant. The bomb disposal squad make regular visits to this and many other farms in the region, stopping off at agreed collection points to pick up the ageing military hardware.

Dirk is philosophical about his lot. When his grandparents took over this ruined farmland rent-free in the 1920s digging up explosives was all part of the deal. It could be worse, some farmers still find human remains.

For the past 12 years Dirk has run a bed and breakfast at the farm. It’s a favourite with military historians and battlefield tourists. He has even converted an old barn into a museum full of shells, bullets, grenades, machine guns, helmets, water bottles, bits of old uniform and the occasional rifles he finds dangling off the bottom of his tractor.

I visited Varlet Farm on a quick side trip from a fascinating tour of the First World War cemeteries, memorials and battlefields of Flanders and Northern France.

I was a guest of travel company Saga and experiencing their Road of Remembrance Tour which starts in Britain’s front-line Channel port, Folkestone, and follows in the footsteps of the millions of World War I soldiers who marched down the old Slope Road to the harbour en-route to the Western Front.

It visits some of the most poignant museums and memorials in Europe and explores the horrors of the trenches and the bravery and sacrifice of the men who fought and died. It was a deeply moving experience.

In Belgium there are great cemeteries like Tyne Cot which holds the graves of 12,000 men and commemorates 35,000 missing, the German war-graves at Langemark and the fascinating Flanders Field Museum in Ypres where you also hear the Last Post being played each evening at the Menin Gate.

In France – where a quarter-of-a-million died on the Somme alone – we visited the vast memorials at Thiepval and Vimy Ridge and experienced a chilling meeting with the past at the extraordinary interactive underground museum at the Wellington Quarry at Arras.

The sites of the battlefields themselves put the war into a graphic geographical context and help explain the horrors of 1914-18.

At the Lochnagar Crater you witness the result of what, before the atomic bomb, was the biggest man-made explosion ever created.

There’s local interest too. The 1st and 6th battalions of the old Dorsetshire Regiment fought on the Western Front for the duration of the war. They lost 4,500 men.

The Road of Remembrance tour visits Hill 60 near Ypres where, in May 1915, the Dorsets, fighting in unspeakable conditions, came under what was only the second gas attack of the war. In the battles before and during the Somme campaign they lost many more men.

In 2011 the regiment (which became the Devon and Dorsets in the 1950s) got its own memorial nearby when volunteers raised funds to erect an eight foot high Portland stone obelisk.

Carved by Dorset sculptors Alex Evans and Zoe Cull, it bears the regimental crest and carries a quotation from Thomas Hardy: “Victory crowns the just”.

The line is from the poem Men Who March Away. Written in 1914 it acknowledges the “faith and fire” that makes soldiers believe that “victory crowns the just, and that braggarts must surely bite the dust”.

Sadly the war to end all wars was far less discriminating than that.

Getaway

Road of Remembrance tour costs from £699 for seven nights.

Starting in Folkestone, it then crosses the channel visiting Arras and the Wellington Quarry, The Somme and Amiens, Ypres and Bruges.

Price includes travel insurance, return coach travel from Folkestone, all breakfasts and five dinners, Step Short genealogy service, porterage, Saga tour manager and expert local guides. Details on 0800 056 6099 or visit saga.co.uk