It is 50 years since the Ken Loach film Cathy Come Home was screened.

Sunday saw the BBC’s 50th anniversary screening of the landmark film, Cathy Come Home. First broadcast in 1966, Ken Loach’s drama about a young mother caught in an impossible, inhuman system, which leaves her homeless, destroys her marriage and ultimately robs her of her children, led to public outrage, a surge in donations to the charity Shelter and the founding of the charity Crisis the following year.

The number of people sleeping rough with a mental health problem has more than tripled over the past five years

I wasn’t born when the film was first shown, yet the sense of hopelessness it conveys, the spectre of the individual smashed repeatedly against the rocks of a rigid, impersonal system is shockingly familiar. Familiar, too, is the misattribution of blame to the individual, rather than acknowledging the wider causes of their situation. Unscrupulous landlords, family breakdown, a negligent employer, and, above all, a dearth of affordable housing are the true cause of Cathy’s predicament and yet she is told again and again to “sort herself out”, as though all that is lacking is an adequate exertion of will.

To hold somebody accountable for a situation they have no power to alter, to increase the pressure by means of threats and penalties if they fail to make changes they have no capacity to make, is a reliable means of breaking a person down. Cathy’s mental health deteriorates and she struggles to contain her frustration, her outbursts regarded as further evidence of personal failing.

It is well established that homelessness has a negative impact on mental wellbeing, and people with mental health problems are also more likely to become homeless in the first place. According to the 2014 health audit, conducted by the charity Homeless Link, 45% of homeless people have been diagnosed with a mental health problem, a figure that is roughly double the national average. And the situation is getting worse. Research this year for the charity St Mungo’s found that in London the number of people sleeping rough with an “identified mental health support need” has more than tripled over the past five years. Over the same period, local authority funding for previously ringfenced services such as supported accommodation aimed at helping vulnerable people, including those who have been sleeping rough, has been reduced by an average of 45%, since the ringfence was removed in 2009.

As it happens, it is also five years since I wrote about Shelter from the Storm (SFTS), a London night shelter where I used to volunteer. I call Sheila Scott, co-founder and chief executive of the charity, for a catch-up. The picture she paints is devastating. Rent rises coupled with job insecurity, zero-hours contracts and benefit sanctions have led to a massive increase in homelessness and in the mental health problems this often leads to.

In addition, SFTS has seen a surge in the number of individuals arriving with more profound mental health needs, people experiencing psychosis, for example, or who are actively suicidal. SFTS receives referrals on a regular basis direct from the wards. “They’ve got nowhere else to go,” says Sheila. The shortage of beds means that staff are under pressure to unblock them, even if this means discharging people to a night shelter. “But what do they do all day?” I ask. “They walk the streets,” she tells me.

And when their mental health deteriorates, as can happen in days, SFTS must try to negotiate with overstretched crisis teams to have them readmitted. There have been several instances of clients being sectioned.

Quite apart from the stress and upset this causes for all involved, it is an absurdly inefficient use of resources, but with services in constant crisis mode, a lack of supported accommodation and waiting lists for specialist services stretching to a year or more, they have few options. Fifty years after Cathy Come Home, it’s high time we invested in providing some.