By ITV News correspondent Sejal Karia
More than a million days of police officers' time have been lost over the past three years because of mental health issues, figures obtained by ITV News shows.
We spoke to one officer whose told us how his work on the frontline led to him developing post-traumatic stress disorder.
"I was unknowingly struggling…my drinking became unbelievable…I just didn't care."
Gary Hayes was on the brink of despair for years.
He had been a frontline officer with the British Transport Police and his day-to-day job was dealing with death.
Sons and daughters who had lost their fathers, husbands who had lost their wives, mums and dads who had lost their only child. In the most horrific of circumstances.
Each life lost, each piercing scream from an anguished relative as he delivered the news their loved one was never coming home, each painful tear shed in his presence are the hidden scars he bears.
But it was the 7/7 London bombings which brought all those mental wounds to the fore.
He had been assigned to a temporary mortuary where the victims' bodies were being brought for identification. He was the acting sergeant, supervising a small team.
With tears rolling down his face he told me: "It was hard you know, I'd seen bodies in various conditions I don't think any of us were expecting to see…the blast injuries were dreadful."
But it was a less visceral sight that became a trigger for his chronic post-traumatic stress syndrome.
When he read a card left by a father to his only child. A son who had been killed in the bombings.
Just days earlier, Mr Hayes had become a dad for the third time. He fell apart.
Breaking down again he said: "This gentlemen come to view his son…and there was just simple words from a father to his son...sorry.
"It just racked me with guilt I was going home to my new son and my other two children.
"I just can't even begin to express...that was tough. That was probably the toughest thing I've had to deal with in my entire life."
He believes mental ill health is widespread among the police service, but the associated stigma is deeply embedded in the culture.
A stigma, Mr Hayes says, can be as disabling as the condition itself.
Freedom of Information figures given exclusively to ITV News show a worrying trend of sickness relating to mental health in the UK’s police service.
Out of 52 forces asked, 27 replied.
The figures show officers and staff across those 27 forces took more than a million sick days over the last three years because of psychological problems.
The Liberal Democrats believe this represents a mental health crisis in the service and has called for immediate government action.
Lord Brian Paddick, the party’s Home Affairs spokesperson said: "The Liberal Democrats are calling for parity both in terms of access to services and in terms of funding between mental health services and physical illnesses and physical conditions.
"Because we're not getting that we see this sort of pressure brought onto people in the police service."
Steve White, the chairman of the Police Federation which represents rank and file officers, agrees investment is vital but so is a change in culture.
He said: "There is support for officers in the service but I don't think it goes far enough unfortunately.
"Because of austerity and cuts over the last few years, we've seen occupational health units being reduced.
"One can understand perhaps to a certain extent why chief officers have had to make those decisions.
"But the evidence we've got now, particularly from the police federation of England and Wales health and wellbeing survey, [which] demonstrates we've got to do more when 65% of officers say in the past 12 months they've gone into work when they have felt they have had mental health issues they haven't resolved. That's deeply worrying.”
Police sick days taken up by mental illness
A Home Office spokesperson said: "We recognise that policing can be a challenging job and welcome the work being done by forces to promote officer health and wellbeing.
"We take the issue of police welfare very seriously which is why we introduced legislation last year to enable the better management of sick and injured officers.
"In November, the Government also allocated a further £1.5m to the mental health charity Mind to enable them to build on their Blue Light Programme which provides mental health support for emergency services staff and volunteers."
One charity, PTSD999 that helps people living with mental ill health across all the emergency services, has said the Lib Dem figures represent only the "tip of the iceberg" and more government funding may not be the magic solution to a deeply ingrained issue.
Simon Durance of PTSD999 said of the figures: "It's just the tip of the iceberg.
"I mean that's just a few of the police forces that have probably got back to you and there's a lot of guys and girls that are still suffering that haven't come forward and spoken about the issues, and spoken about their problems just in fear of losing their job or being branded mentally ill.”
He added: "It's costing the police force and ambulance service millions and millions of pounds by not dealing with it.
"If you imagine you've got a police officer or a police woman whose gone off sick it's long term sick, so those guys are off, you're paying for these guys, you've lost those people out the police force, you've lost policing.
"And these guys’ condition is getting worse and worse and worse…it's key to get these guys and girls looked after diagnosed early on and then treatment and support it's hugely important and that'll save the police force millions of pounds it'll pay for itself in the long term."
Mr Durance estimates each police officer costs a given force around £53,000 a year.
If they were to be off sick for six months, it would end up costing the force £26,000 for that period.
If 1,000 people are ill for just one month in that same force, it would cost £4.5 million, which Mr Durance said would be a conservative estimate.
However, he adds, if out of a workforce of 40,000 you have 200 people on long term mental health sickness that would be around 73,000 policing days lost.
He conservatively estimates it would cost that police force around £10 million pounds.
Gary Hayes believes the man he once was, has been lost. But with the right support, he thinks other police officers need not suffer in silence.
We tend to spend a lot of time…looking at making sure we get it right with the general public around mental health and suicide prevention…but we miss the obvious, we miss looking at our own officers.