David Cameron's comments have sparked waves of discussion about whether Britain can really be thought of as a "Christian country", the question on people's lips being 'what actually makes a country Christian or not?'.

The simplest place to start would be something like demographics. In Coriolanus, Shakespeare said: "What is a city, if not its people?"  And many believe that in this debate, the word 'city' can easily be replaced with 'country'.

Whether the British people are mostly Christian is a difficult one to answer. In their letter published in the Telegraph protesting the Prime Minister's comments, a group of more than 50 notable secularists said: "Repeated surveys, polls and studies show that most of us as individuals are not Christian in our beliefs or our religious identities."

The picture of Christian affiliation in Britain is indeed complex. The 2011 census figures show 59 per cent of the country self-describe as Christian.  In the same year, a YouGov poll commissioned by the British Humanist Association (BHA) found that while 61 per cent of respondents listed themselves as 'Christian', 48 per cent of that group said that they did not believe that Jesus Christ was the Son of God, or even a real person who came back from the dead.

The secularists may have a point when it comes to people's religious beliefs, if not their identities. Most Britons might call themselves Christians, but whether they have faith in Jesus is something very different.

As Canon Chris Sugden, of Anglican Mainstream, points out: "People are Christians not because they live in a particular state/geographical area/cultural space or with a particular ancestry/history but because they have personally accepted Jesus Christ as their Lord and Saviour."

If we shift our gaze from belief to practice, it's easy to see why secularists can confidently finger wag. The Church of England's official figures estimate that approximately 800,000 people would have attended one of their 16,000 churches last Sunday. That represents only 1.27 per cent of the UK population.

Even if other denominations and church groups are included, estimates put the number of Christians who regularly attend church at around 2.5 million, just over 4 per cent of the population.

However, while a nation may be its people, it is also what its people have built in its institutions and culture. In this regard, there is still much to be said.

Looking from the perspective of a missionary seeking to better establish the Christian faith in this country, Israel Olofinjana, a Nigerian-British Baptist missionary currently leading Woolwich Central Baptist Church in South East London, notes that at the cultural and institutional level, there is still a great deal of visible Christianity.

"The ceremonial head of our country is still the Queen, who is a Christian, we still have bishops occupying important seats in the House of Lords, and the chaplain to the Speaker in the House of Commons still offer prayers before the start of any session. The national flag as well as the English flag has a big red cross on it."

Professor Linda Woodhead from Lancaster University holds a similar view. Author of 'Religion and Change in Modern Britain' and 'A Very Short Introduction to Christianity', Professor Woodhead accepts that while many may be leaving the Church, they have not left church culture behind.

"In culture and institutions Britain is more Christian than not. What is happening is that people are leaving the churches, not faith."

She also notes that many of the those with substantial amounts of power in modern culture do maintain a Christian identity which continues to shape our culture now: "In its elites, such as the public schools and Oxbridge, Britain is still very much Christian."

In the corridors of government, however, laws on issues such as divorce, abortion and marriage have been liberalised beyond Christian teaching and sat at odds with many Christian groups.

John Martin, general secretary of the evangelical Anglican group Fulcrum notes: "Over many years the secular has continually won the day over Christian convictions in Parliamentary debates."

Where Christian groups do manage to successfully convert lobbying into policy victories, this may not be welcomed by the wider population. A 2006 Ipsos MORI poll found that religious leaders topped the list of groups that the general public felt had too much influence.

Dr Michael Martin, Director of the Critical Religion Research Group at the University of Stirling, wonders whether it is more accurate to think of Britain as a part of Christendom rather than as a Christian country.

"Britain is not a Christian country, but it is a country marked by Christendom, in other words, a country that has emerged from a close entanglement between Church and State, the vestiges of which are still with us, for example, bishops in the House of Lords, the Anglican Church as the established church in England, the privileged position of the Church of Scotland in Scotland and so on."

However, he believes that any loss of status is something the Church should welcome rather than fear as in his view, the current situation limits the Church's ability to impact society and gives the politicians a great deal of control.

As evidence of this, he notes the deep irony that on the same day as David Cameron made his comments about the UK being a Christian country, his constituency office made something of a blunder when it called the police to intercept a bishop and a vicar who were trying to deliver a letter asking the Government to do more to fight hunger and poverty in the UK.

Recent specific Christian political victories may be few and far between, but Canon Sugden agrees that the very foundation of our legal system itself bears a Christian hallmark: "This Christian foundation affirms and underpins the infinite worth of every human being.

"The freedom and responsibility of each person to choose freely what they believe, to be free to give public expression to their beliefs and faith, to recognise the diversity and respect the integrity of the different faith communities and to live peaceably in mutual respect."

The Bishop of Swansea and Brecon, John Davies, is also asking himself some questions about how Christian Britain really is. Christianity might be present at many levels of national life, but whether that Christianity is truly engaged with is a very different thing.

"Prayers often characterise all manner of meetings and gatherings, from Grace said at a variety of meals, to prayers beginning meetings of parliament and other organs of government, and the legal requirement for there to be a daily act of collective worship.

"But can the 'what does exist' really add up to mean that the majority of people in Britain would agree that 'Jesus Christ is Lord'?"

His thoughts echo the BHA poll in that while many people like what Christianity stands for, they are not sure what they think about actually following Christ.

"I suspect that [most British people] would applaud national life and individual lives lived by principles which are consonant with much of Christian belief and which may even have some roots in Christian belief; they may even like to see places of Christian worship open and used with regularity - a kind of vicarious but non-participating religion.

"I'm not sure that this makes Britain a Christian country per se. Goodness and loving-kindness pre-date the church."

Reverend Yemi Adedeji, director of the One People Commission of the Evangelical Alliance, suggests Britain's Christian identity is bound up not only in what has been built at home, but in what it has been shared with the rest of the world.

"The sacrificial effort of those who travelled to many parts of the Commonwealth, to take the Christian message by helping to alleviate poverty and establish the Christian faith as missionaries, are enough to convince the humanist that Britain does indeed have a Christian heritage," he said.  

Susie Leafe, director of the evangelical Anglican group Reform, thinks Britain has become "post-Christian" in its identity in the modern age.

Nonetheless, this does not mean Christians should rest on their laurels in the face of determined efforts to diminish Christianity's presence in public life.

"We need to acknowledge that we have inherited laws and a culture shaped by Christianity but we are in danger of frittering away our legacy without a coherent alternative."

While the Church could feel negative about the challenges, Mr Olofinjana believes them to be a great opportunity for the Church: "The good thing about the marginalised position that Christianity is in Britain today is that we are better placed, may be ever than before to reach out to people in our nation."