When Jonathan Sacks was a teenager he went to his local MP for help with an A-level essay.
It was the start of a long-standing friendship with the then Margaret Thatcher, which was to help shape the view of politics of the young Jonathan, now Lord Sacks, the Chief Rabbi.
“I was doing an essay on proportional representation once and I went to her - I’m 17 years old - she looks at me and says” - he leans forward with narrowed eyes and breaks into a high-pitched imitation of his former MP - “.'you’re not a liberal, are you?’”
He breaks into a deep laugh, concluding: “She was formidable.”
That friendship, however, - and a later one with Gordon Brown - did not shake a conviction Lord Sacks developed that religion and politics do not mix: “Never confuse religion and politics,” he says. “If you do it is bad for both.”
All the more extraordinary then that he marks his retirement a week today after 22 years as de facto head of the Jewish community, with an interview which covers some of the most contentious political topics; gay marriage, the Middle East, and “trolling” on social media.
Lord Sacks’s view is that he is carrying out a duty of faith leaders to create a “moral climate” in which politicians can make their decisions.
Among his chief concerns is the breakdown of marriage. He and his own wife, Elaine, 64, married in their early twenties and Lady Sacks, who was first a radiographer, has worked alongside her husband, teaching and supporting a series of Jewish charities.
The couple have three children and seven grandchildren.
“I used every opportunity I had in broadcasting, in writing I was doing for the press, and internally within the Jewish community, to strengthen marriage,” he says.
He believes the Government is not doing enough for marriage, and says that marriage should be recognised in the tax system - a Conservative commitment strongly opposed by Labour and the Lib Dems.
Lord Sacks dates the decline of the institution to the 1960s and a generation which failed to hand on their own values to their children.
“It seems to me that the breakdown of marriage seemed like a tremendous liberation. We were there in that revolution and at the time it seemed to be 'all you need is love’ and nothing else.
We live to see, 50 years later, the full cost of that, of an entirely new kind of child poverty that has a lot to do with single parent families.
“No one wants to lay a burden of guilt on anyone who bought into the cultural attitudes of the 60s but the fact is their kids are suffering.”
Sitting in the lounge the terraced home in St John’s Wood, north west London, that is his official residence, Lord Sacks says that the practical effects of marriage breakdown are clear: increasing numbers of people are living alone, which has particularly affected young couples wanting to get on the housing ladder for the first time.
“I find it morally unacceptable for hard working young people to be unable to afford a home, in at least the same town in which they work.”
Standing up for marriage has been a theme of his since he became Chief Rabbi, using his installation speech in 1991 to warn that divorce had become “an epidemic”.
But his voice has been noticeably absent as Christian, Muslim, Sikh and Buddhist leaders have all vociferously opposed the Coalition’s legislation introducing gay marriage.
In June last year Lord Sacks issued his only official statement on the issue, a formal submission to the Government’s consultation, from the London Beth Din - the Chief Rabbi’s court - which reiterated traditional orthodox teaching that homosexuality is against Jewish law.
Among British Jewry the statement reinforced battle lines between denominations, with the Reform and Liberal movements supporting of gay marriage.
Although the Chief Rabbi has come to be seen as head of the entire Jewish community of around 260,000, it served as a reminder that he formally leads only the United Synagogue, a group of 61 Orthodox communities with a total of 70,000 members, as well as a further series of synagogues which come under the banner of the United Hebrew Congregations.
After the statement was released, the shutters went down. In none of his 18 broadcasts on Thought for the Day since last June has Lord Sacks mentioned gay marriage.
He has similarly maintained a silence in Parliament and the national press on the issue - until now.
“There is a Talmudic principle that says, 'Just as it is a duty to say that which will be heard, so it is a duty not to say that which won’t be heard’. In other words there is such a thing as a sense of timing, of moment.
And I actually felt that this was not a moment when our particular message could be heard.”
Effectively distancing himself from other prominent faith leaders, Lord Sacks says he was “confident” that the Government provided “cast iron guarantees” that religious freedom would not be curtailed by the legislation, which eventually received Royal Assent last month. Any further intervention risked hurting the gay community, he says.
“I have fully understood the fear that gays have of prejudice and persecution,” he says.
“I fully understood, and I mention this pretty much every year, that gays, not just Jews, were sent to the concentration camps, and I did not want to become a voice that would be caught up in a very polarised debate and be seen to be heartless towards the gays in our own community.
I am not heartless towards them,
I really seek to understand them and they seek to understand where I am coming from.”
It is a far cry from the rhetoric of other religious leaders, particularly Cardinal Keith O’Brien, the now disgraced former head of the Catholic Church in Scotland, who was accused of “whipping up prejudice” with his claim that the proposals were “madness” and a “grotesque subversion of a universally accepted human right”.
Asked about the language used by same-sex marriage’s opponents, Lord Sacks does not refer to Cardinal O’Brien or any other leader by name, but issues a pointed rebuke. Nobody can get “nuance out of a sound bite in a deeply polarised and impassioned and divisive debate”, he says.
It is likely to be his final word on the matter but in retirement - he will be replaced by Ephraim Mirvis, 56, a South African-born former chief rabbi of Ireland - he will turn to a wider mission: the evils lurking on social media.
Lord Sacks, who owns an iPhone and an iPad, has used his own Facebook, Twitter and YouTube accounts to reach Jews in Britain and abroad.
New technology, he says, widens access to knowledge, and knowledge “is the source of human dignity in Judaism”. But the anonymity the internet provides to its users can also have a corrosive effect.
“We are worried about the social media because you can post abusive comments without the person being in your physical presence. That anonymity and that distance mean that the internet is one of the great carriers of prejudice and paranoia, and I don’t take it lightly. “
So what can be done to protect people from the this side of the internet?
“I think you have to bring it under the general ambit of hate speech, and it’s a combination I think of extending the kind of things that you have on the press to the hosters of websites,” he replies.
“It’s very difficult, but it does mean they have to be vigilant and they have to take hate speech off their websites as soon as they discover it.”
Companies that allow abusive speech should be “named and shamed”, he says, pointing out that public pressure has prompted Ask.fm, founded by two Latvian brothers, to introduce new controls after it was linked to a series of teenage suicides.
However the cause which he discusses with the deepest concern of all is the persecution of Christians in the Middle East - a plight, he argues, which is getting virtually no attention in public life.
“I think this is a human tragedy that is going almost unremarked. I don’t know what the name for this is, it is the religious equivalent of ethnic cleansing.
“We are seeing Christians in Syria in great danger, we are seeing the burning of Coptic churches in Egypt. There is a large Coptic population in Egypt and for some years now it has been living in fear.
Two years ago the last church in Afghanistan was destroyed, certainly closed. There are no churches left in Afghanistan.
“Between half a million and a million Christians have left Iraq. At the beginning of the 19th century Christians represented 20 per cent of the population of the Arab world, today two per cent.
This is a story that is crying out for a public voice, and I have not heard an adequate public voice.”
It is striking that this is an issue which does not directly involve Jews at all.
But being Jewish, “you cannot but feel this very deeply and personally”, he says. “I think sometimes Jews feel very puzzled that Christians do not protest this more vociferously.”
He compares the violence faced by Christians in Egypt, Syria and Iraq to the mass exodus of Jews from Arab countries in 1948, when the establishment of the Jewish state was followed by the persecution of Jews in countries including Egypt and Libya.
Those who remain today are “very small residual communities living in fear”, the Chief Rabbi says.
Aside from a debate 18 months ago in the Lords led by Dr Rowan Williams, the then archbishop of Canterbury, political and religious leaders have failed to respond adequately to the problems Christians are now facing in the same region, Lord Sacks suggests.
“I don’t know why people don’t speak more about it. I would hope to find the opportunity to do so, I’m just not sure when and how. It is a very, very scary situation.”
The outgoing Chief Rabbi’s stark warning recalls his insistence that it is not for him to get involved in the specifics of politics, but instead to create a “moral climate” in which they can operate.
There is one element of politics in which he will not meddle at all: the likelihood of Ed Miliband, the first Jew to lead Labour, becoming prime minister.
“Couldn’t possibly comment on that, minister! All I can promise is the next prime minister will light Chanukah candles. More than that I can’t promise.”