Winston Churchill, Abraham Lincoln and Charles Darwin – undeniably figures who have helped shape modern life.

But each battled demons which if they had admitted today may well have stopped them from doing their jobs – or at least left them shunned among their peers.

Why can people at the very top of their field not have the odd run in with the “black dog” as Mr Churchill used to refer to his depression?

Mental health is often – understandably – brushed under the carpet by sufferers afraid that if their condition was made public their image would be irreconcilably tainted.

Countless people lie to their employers when they suffer a bout – how many of those colds and throat infections are actually far more serious? - and discrimination against those who are brave enough to tell the truth ratchets up another level.

But last week in parliament something incredible happened – two MPs stood up during a debate on mental health and admitted their own battles. Labour’s Kevan Jones and Tory Charles Walker think it is time for Britain to change. For years they kept their illnesses secret but during an emotional session the pair spoke about their problems.

Mr Jones said he had suffered a deep depression in 1996 and admitted the decision to speak out now had been one he had wrestled with: “Like a lot of men, you try and deal with it yourself. We are... in politics designed to admit that somehow if you admit fault or frailty you are going to be looked upon in a disparaging way, in terms of both the electorate and your peers as well.”

Speaking to East meets Westminster, Mr Walker told how his condition, obsessive compulsive disorder, had permeated his whole life but never held him back professionally.

“What I did was not brave – it just needed to be done. It might have been brave 20 years ago – or foolhardy – but now it just needed to be done.

“My condition is very benign at the moment. I have a few little rules … a few little things I do - but for some people it is far more serious. At times it is darker than it is at the moment but I am blessed that I have been able to live a good life. I work to the rule of four and do everything in evens. And sometimes a voice in my head blackmails me into doing things – I am a keen angler, for example, and it often suggests that if I don’t do something that next big catch might wriggle off the hook.

“When I took to my feet the only people that knew what I was going to do were my family and office staff. The response I have had from the public has been incredible. People don’t credit the British public with enough intelligence – I am confident things are changing for the better.”

This is politics at its most vital and heroic. All the back-biting, the secret briefings against opponents – often in the same party – and the bad headlines are worth it when politicians take a personal risk to help those who elected them.

Statistics show one in four people is directly affected in ways similar to Mr Jones and Mr Walker – that is more than 150 elected members.

Mental health charity Mind has reported a spike in the number of people asking for help. In East Anglia between October last year and April, 766 people rang their helpline. In total this is an increase of 18%.

There has also been an increase in the number of people asking the charity for legal advice – often this involves disputes with employers about time off.

Whether more people are suffering from depression or if help is now more easily available is open for discussion. But on the back of these MPs brave words hopefully more will follow and figures from high profile professions will also speak out as Gavin Barwell’s private members bill – which prompted the debate – makes its way through the legislative process.

Tony Blair’s former director of communications Alastair Campbell’s breakdown in 1980s was widely known before he took the job at No. 10. He took the decision to be open about it from the start.

“I was already quite well known as a journalist and it would not have been possible to hide it,” he told this column. “Then when I started working at No. 10 people started writing about it.

“Every day people come up to me and thank me for talking about it and I think there is actually a lot of sympathy for people who suffer.

“The MPs standing up in parliament and saying they have these problems is a massive moment – but sadly I think we still have a long way to go. But I do hope we will be able to look back and say ‘this was a huge step towards the tipping point’.

“It is more about culture than legislation in many respects. People need to see those in power and those with influence admitting to being sufferers, from there will come understanding. But people still feel when they ring their boss feeling ill they cannot tell them the truth. And each time someone lies the issue is not tackled.

“My breakdown and dealing with it made me stronger. It made me more capable to do the job I went on to do in No. 10.”

Talking about these problems will not cure them. But understanding them will beat the taboo that is so often as hard to deal with as the illness itself. And parliament can be proud of any role it plays.

Mr Campbell is an ambassador of the Time to Change campaign which is fighting to empower people to be honest about mental health problems. To find out more log on to www.time-to-change.org.uk. For more information about mental health issues call the Mind infoline on 0300 123 3393.

Richard Porritt is on Twitter @Porritt.