More soldiers failing drug tests on foreign deployments
The equivalent of a battalion of soldiers failed drug tests on a foreign deployment during the past five years.
The number failing had risen from 80 in 2012-13 to 110 in 2016-17, a BBC freedom of information request found.
Experts say high frequencies of deployments to countries where drugs are more easily accessible to soldiers could explain some of the rise.
The failure rate has more than doubled from one in 240 to one in 110, but the number of soldiers deployed has fallen.
The Army says it has increased the number of soldiers being tested, and has a zero tolerance attitude to drug test failures.
Drugs tested for include recreational drugs such as cocaine and cannabis, as well as performance enhancing steroids.
'Stress and boredom'
Jacquie Johnston-Lynch, head of service at veteran addiction charity Tom Harrison House, said one client had taken drugs while deployed abroad to deal with boredom.
"One told me the party lifestyle was such a part of being stationed overseas. They regularly took recreational drugs just to relieve stress and boredom," she said.
For others, it was injury that led to addiction.
"I was taking copious amounts of painkillers for an injury I'd got in combat previously, so any opportunity I could I was swallowing opiates," said another veteran.
"I was addicted but not really willing to seek any help because it would've been frowned upon for sure," he added.
A total of 470 soldiers failed drugs tests from 2012-13 to 2016-17.
While the Army tested 10% of its deployed soldiers in 2012-13, this rose to 55% in 2016-17. But this alone does not account for the higher number of drug test failures because the number of soldiers being deployed has fallen sharply over the same period.
The Army says soldiers testing positive on non-combat overseas deployments, such as in the Baltics, Brunei or Canada, would usually be kept in the country until their dismissal was complete.
But those that failed drug tests on combat deployment, such as in Iraq and Afghanistan, are usually returned to the UK.
'Running very hot'
Peter Quentin, land warfare research fellow at the Royal United Services Institute, said the high-tempo deployments British soldiers were currently engaged in could explain an increase.
"Parts of the Army are currently running very hot, being deployed on training missions and exercises, with some individuals deployed several times a year," he said.
"These deployments are not the high-intensity combat operations we saw in Iraq and Afghanistan, but to places such as the Baltics.
"It may be easier for those soldiers inclined to take drugs to access them there, and this could explain some of the rise."
He also noted that some of the drug test failures would be for soldiers caught taking steroids.
"Steroids are a particular problem for the Army, because soldiers taking them may naively be trying to get fitter and stronger to better perform as soldiers," he said.
"The Army puts a lot of effort into educating soldiers as to the health and employment issues with taking steroids, so it is not just about punishment."
Prof Sheila Bird, from the University of Edinburgh, said the Army tended to be efficient at testing for drugs and acting on intelligence to target those suspected of taking them.
When they had discovered a higher test failure rate on Mondays and Tuesdays, they had shifted testing days to detect soldiers taking drugs at weekends, she said.
"However, soldiers do sometimes try to game the system," she said.
"Back in 2008, the test failure rate for cocaine went down, but this was due to soldiers switching to the then legal drug mephedrone.
"This has similar effects to cocaine, but was legal and couldn't be tested for by the Army."
However, she said, sometimes this gaming did not work.
"On one occasion, around 20 soldiers from a Scottish battalion tested positive after a period of rest and recuperation while on deployment in Belize.
"They hadn't factored in the potency of the cocaine they had been taking.
"It was much purer than that available in the UK, and they underestimated how long it would stay in their systems."
A spokesman for the Ministry of Defence said: "Drug misuse is not tolerated in the armed forces.
"It reduces operational effectiveness, and soldiers caught taking drugs can expect to be discharged.
"By conducting over 87,000 tests per year, drug misuse is significantly less prevalent among service personnel than in corresponding civilian demographic groups."