Workers pass an electronic billboard showing the 1919 painting Gassed by John Singer Sargent, which hangs in the Imperial War Museum.

London - This year’s centenary of the outbreak of the First World War is pushing up the value of memorabilia, raising fears that many amateur collectors or inheritors of family heirlooms may be underinsured.

Matthew Haley, head of books and manuscripts at auctioneer Bonhams, says that based on other recent military anniversaries, the value of most First World War memorabilia will rise by between 20 and 50 percent.

He says: “Although there is a lot of First World War memorabilia about, because so many people were involved, there is also a lot of interest. Some of it can be very valuable.”

He cautions owners of items such as medals, manuscripts and uniforms to ensure that they have these items properly valued, and to check that their home insurance covers their collections.

He says: “Many policies treat a collection as one item, so it can be easy to come up against limits on what the insurer will pay out.”

Military memorabilia experts agree that it can be difficult to work out what items are worth.

“First World War items are very strange in the way their value is perceived,” says Steven Bosley, of Bosleys Military and Medals Auctioneers, a specialist auction house based in Marlow, Buckinghamshire.

“Take a soldier’s tunic. They all look very similar but can be worth between £300 and £400 or all the way up to £1 000 depending on the insignia and historical provenance.”

Items can be valued at auction rooms around the country and the National Association of Valuers and Auctioneers has a full list on its website at nava.org.uk.

Interest in the artefacts comes as London’s Imperial War Museum reopened after a spectacular £40-million transformation.

And Bonhams is holding an auction dedicated to First World War memorabilia in October, with the catalogue already including some items that could prove to be unexpectedly valuable. A group of medals awarded to Brigadier General GPS Hunt have an estimated price of between £3 000 and £5 000, while a memorial plaque given to Minnie Johnson, of the Queen Mary’s Army Auxiliary Corps, has an estimated price of between £1 800 and £2 200.

There were thought to be just 600 memorial plaques given to the families of women who died in service in the Great War. “Items with stories tend to fetch more,” says Bosley. “If you can prove the historical provenance of something and the fact that it was actually used in the war, and where, that will add to the value. The most valuable items tell us things that we didn’t know.”

Given the anniversary, some items in upcoming auctions are expected to far exceed their guide prices. At Bonhams, a set of letters and caricatures from German soldier Albert Heim fetched £14 190, against a guide of between £3 000 and £5 000, while a letter describing the 1914 Christmas Truce from an anonymous soldier calling himself ‘Boy’ fetched £14 400 against an expected £300-£400.

Whether people are planning to keep or sell their collections, experts say that it is important to have them valued. Kevin Pratt, insurance expert at comparison website MoneySuperMarket, says that although many people can cover their collections as part of their home insurance policy, they need to be aware of the small print.

“You should check your policy details to see how they treat collections. For example, you might have a dozen medals in your collection, but the policy will treat them as a single item, rather than pay out the separate value of each one,” he says.

“A standard policy will usually impose a single item limit, which is the maximum amount it will pay out on the loss of any particular item. This is usually £1 500 or £2 000, but you should check your policy for details. So if you lost something worth £3 000 but had a £2 000 limit, the policy would only pay £2 000.”

Lindsey Lee, from insurance broker H W Wood Limited, which operates a collection-specific insurance policy called ‘Collect and Protect’ says enthusiasts should also be aware that if they are planning to transport their memorabilia to shows or talks during the anniversary period they would not be covered under a standard insurance policy if items were lost or stolen en route or outside the home.

“In some cases insuring your collection on your home policy is fine, but in others a specialist policy is more appropriate,” she says. “Many amateur collectors have a good idea of what their items are worth, but values are going through the roof.

“The anniversary is driving some young people towards collecting memorabilia as a form of pension.”

Lee adds that no matter what insurance policy collectors have, they should keep a photographic record of their collection somewhere other than at their house.

“The last thing you want to be doing after a disaster is wondering what was in your collection and having to prove it.” - Mail On Sunday