I started in this new post on 1 August. I'm responsible for implementing the Commissioners' ethical investment policies and responsible investment commitments across their £6.1-billion portfolio. 

Before that, I was secretary to the Church of England's Ethical Investment Advisory Group (it's known as the EIAG), which advises the Church Commissioners, the Church of England Pensions Board, and the CBF Church of England Funds on ethical investment.

The Commissioners' first legal duty is to maximise the return on the assets of which they have stewardship. They do this to help fund the ongoing mission and ministry of the Church, from clergy pensions, cathedral stipends, and bishops' office costs to mission training schemes and grants to parishes for everything from youth workers to projector screens.

The benefits of responsible stew-ardship are evident throughout the life of the Church. But it is vital to be alive to the potential for both positive and negative impact from investment, and that's where ethical investment comes in.

I'm concentrating at first on talking to investments staff at the Commissioners, and their asset managers, about how ethical factors, including social and environmental factors, are integrated into investment decision-making and monitoring. Then I want to make some recommendations on how to take ethical and responsible investment forward at the Commissioners. I also want to communicate everything the Commissioners do in this area better.

There's a lot of misunderstanding about ethical investment. The Commissioners invest in the same messy and ambiguous world we all live in. While we avoid investing directly in sectors that most people think are inappropriate for church investors - such as defence, tobacco, and gambling - there will always be assets in which we are invested where there are controversies. 

We turn this to positive effect through the engagement programme of the EIAG. The EIAG annual reports give numerous examples where this engagement has had a positive impact. For instance, this year the EIAG announced that the three biggest UK-listed supermarkets, Tesco, Sainsbury's, and Morrisons, had all published new alcohol policies acknowledging the harm that alcohol can cause.

On the micro-level, through the Bath & Wells link with the Anglican Church in Zambia, and their visits to the Copper Belt there, we raised concerns about sulphur-dioxide pollution from Glencore's smelter. They have now upgraded the smelter to make it more efficient at capturing sulphur-dioxide emissions - 18 months earlier than planned.

No one wants the C of E being critical as an investor, because it can result in negative publicity. And companies are genuinely interested in what the Church has to say, because it can be a little bit ahead of public opinion and can act as an early-warning indicator on changes in society's attitudes.

Of course, it would be safer by far not to invest, and to put it all in the bank. But this wouldn't yield anything near the returns we have achieved. Anyone familiar with the parable of the talents will be alive to the parallels. 

Investment is ethical. It allows families and organisations, including churches, to put their money to work, benefiting them and society. 

The Christian position on usury has developed over the centuries. Calvin and his church in Geneva looked at it in a more modern context, and thought that money lent for setting up new businesses was, on balance, compatible with Christian discipline. That seems to be the centre of gravity of opinion in the Church now: that money lent for mutual benefit is OK. The EIAG looked at this when it formulated its high-cost lending policy; so we will invest in high-street banks, but not in doorstep lending, or payday-lending companies. 

The problem with Wonga last year was that it was included in a wider pool of funds. The Commissioners are able to apply ethical exclusions where they make direct investments, but there are some areas of the market (the portfolio is worth £6.1 billion) where you have to invest in pooled funds, and individual investors cannot normally insist on ethical exclusions.

In the case of venture capital, it's trickier still, as you give the money to a venture-capital manager, and you don't know where he or she is going to invest it. 

We think venture capital is a good thing - creating new businesses and jobs - but there is very little pure black or white in investment.

All the meetings of the Commissioners' board and committees begin with prayer. The range of experience in the discussions which follow is tremendous. It's amazing to have meetings where bishops, theologians, and parish priests collaborate with city experts, private-equity executives, and property investors to make decisions on how best to steward the funds. 

The Commissioners are great investors: their target is to make a return on investments of the Retail Price Index plus five per cent. It's a target that they have beaten over five, ten, and 20 years. My job is to help them to continue to be great Christian investors. It's a job that's never finished. 

I've got accounts with both a bank and a credit union. Christians who haven't looked for a credit union to join should definitely do so. We need a much bigger credit-union presence in this country. Institutionally, the Church is showing a lead on credit unions, and we need to take up the challenge as indi-viduals, too. 

I don't think it is unchristian to talk about our money as much as un-English. It's not an attitude replicated around the world.

Jesus spoke about money more than many other subjects; so we shouldn't be reticent to follow that example. In England, Christians are at least great at talking about how to give and be generous with money, and that's very important. 

Recently published figures show that parishes across the country raised a record amount of £929 million in 2012 to fund the ministry and mission of the Church of England. Giving by churchgoers is by far the biggest income source of the Church, much more important than anything the Commissioners contribute. The Commissioners' contribution is 15 per cent. 

I'm married to Fiona, and we have two girls aged seven and ten. I was born in Chester, but my father got a job in London when I was nine; so I'm a Londoner now. Fiona is from the Outer Hebrides, and we love our annual visit to Isle of Lewis. 

I really enjoy family time, but when being in an all-female household gets too much, to the chagrin of my eldest, I slip off to a pub showing Sky Sports, or to Stamford Bridge itself to watch a Chelsea game. 

I love travelling, and I spent the first 15 years of my career in the Foreign Office. I joined as a graduate entrant and became a diplomat, working in Oslo and Zagreb. But that itinerant lifestyle wasn't so attractive to us as a family, with the prospect of frequent moves and boarding schools, and so on. And I'm quite a curious person: I didn't want to stay with one employer all my life, and I was interested in investments. 

In Europe I'm particularly fond of Italy. It has history, a good climate, and great food, wine, and coffee, which is enough to keep me happy for a very long time.

I just like to stay fulfilled, and can imagine lots of ways of doing that. I could imagine doing plenty of things in the future, whether going back to foreign policy once the kids have grown up, or starting a business in the Outer Hebrides, if I can persuade Fiona to go back. My favourite sound is the sea, lapping waves on a beach. Bliss. 

I think two school friends influenced me most. Steve taught me how to follow my principles. Nick opened my eyes to London and to exploring the world beyond. 

I really enjoyed Siddhartha by Herman Hesse. It tells the story of the spiritual journey of a man who adopts Buddhism, then throws himself into worldly success, before finally finding peace and enlightenment as a ferryman. It is a short and beautiful read which has stayed with me. 

At the moment, I pray for my 98- year-old grandmother, who is in a care home. I pray for peace for her now that she is close to the end of her life. 

Fiona's father, Angus Macleod, died just before we started going out. If I could be locked in a church with him, I would love the opportunity to meet him and to know him a little. He had such an interesting life, coming from a crofting family on the west coast of Lewis, to have a very successful career in education, and raising a wonderful daughter.

Edward Mason was talking to Terence Handley MacMath.