Horse chestnut trees have been in Britain for centuries
The future of Britain's horse chestnut trees could be under threat because of a disease which has swept across the country, experts say.
They are an iconic sight, found in hundreds of churchyards, parks and gardens.
And scouring the ground beneath the trees for the biggest and best conkers is a tradition which stretches back centuries.
Many people have fond childhood memories of their playground conker battles.
Striking an opponent's conker to find the toughest is an age-old game.
But a newly discovered fungus, causing many "bleeding cankers", could make this a rarer sight in future.
Cankers are an area of dying bark, like sores which ooze liquid, and have existed on horse chestnut trees for several decades.
But scientists are concerned that an infectious new bacteria (Pseudomonas syringae pathovar aesculi) is causing most of the cankers found today.
Moths thought to have spread to the UK from Greece and Macedonia are also destroying the leaves of many horse chestnut trees, as is a fungal infection, leaf blotch.
This week it emerged that the situation has got so bad that it is threatening this year's World Conker Championships, in Ashton, Northamptonshire.
People from around the world take part in the conker contest
Every year 5,000 conkers from the area are sorted for shape and size - contestants are not allowed to take their own.
But this is the first time in the competition's 44-year history that its conkers have been affected by disease.
John Hadman, secretary of Ashton Conker Club, believes it is an "extremely worrying" problem, but said he was hopeful this year's event would happen.
"We will send out an SOS. We've already had offers of conkers from as far as Aberdeen," he said.
"We need them a specific size and shape - about one-and-a-quarter (3.2cm) to one-and-a-half inch (3.8cm) diameter - and fairly round.
"We're always optimistic. We've had various threats before, but I must admit we are getting more apprehensive now.
"I can't imagine that the horse chestnut will become extinct, it would be a disaster if that did happen."
So could it be as bad as Dutch elm disease, which wiped out millions of UK elm trees from the late 1960s onwards?
The Forestry Commission carried out a widespread investigation earlier this year to assess the extent of the cankers' spread.
It found symptoms of bleeding cankers in half the trees it surveyed.
Land owners have been urged to look after their trees
Roddie Burgess, head of the Forestry Commission's plant health service, said: "We do not yet have the complete picture.
"For example, we don't yet know the total number of horse chestnut trees in Britain affected by bleeding cankers.
"There is a limit to what can be done to combat diseases of trees.
"The key things are to encourage tree owners and woodland managers to practise good woodland management and tree care to ensure maximum tree health.
"The healthier a tree is, the better it is able to withstand attacks by pests and diseases."
The commission thinks it is "too early to say" if it is the beginning of the end for Britain's horse chestnut trees.
But Mr Burgess added: "There are still hundreds of thousands of healthy horse chestnut trees in Britain, so there should be plenty of conkers to satisfy demand for the foreseeable future."