The Missionary: Martin Street works as a London City Mission (LCM) missionary in Battersea, on the south bank of the Thames. He grew up being taken to church by his mother, but it was while he was at university in Cambridge that he first began to engage with Christianity.

"I was really blessed with people opening up the Bible there," he said. "It was the most wonderful thing in the world to understand the love of Christ for me. . . Ever since then I have had this passion for bringing the truth of the gospel to the man on the street."

After six years as an electrical engineer, he decided to give it up to work for the Church.

Considering ordination, he studied at theological college, but came to believe much of the Church had lost touch with both the scriptures and the needy.

"We have lost confidence in the authority of the scriptures and we have failed the poor and the marginalised of our society. My fear is that's where the English Church has ended up - upper-middle class circles without the gospel."

So, instead, he ended up with LCM, working on deprived estates in south London. He says he wanted to be in the places that Jesus would go: "In 21st-century Battersea, that often means hanging out in a tower block in a draughty hallway, speaking lovingly to someone on the doorstep, and reaching out . . . with grace."

Much of his job is simply going into people's homes and chatting with them for a long time over cups of tea. Mr Street seeks out the marginalised, the isolated, and the friendless, and tries to build relationships.

Embedded in a local church, he has set up a lunch club for the elderly, and targets the immigrant communities living in Battersea. Those living with mental-health problems are also among his regular list of contacts.

But he is brutally honest about the uphill struggle of his work. "To be perfectly honest, most days I tend to come back and think 'I did a pretty bad job,' or 'That was exhausting or discouraging.'"

"Just now we have had a men's evangelistic night and it's routinely mayhem - just trying to get them to get along with each other is quite a challenge some times. They all think everyone else is an idiot."

But, every now and then, he sees a small step forward that makes the battle worth while. He described how he read a Bible passage with one man he knows who has long-term depression. The Holy Spirit "turned on the lights", he said, and made sense of the hope the passage was talking about.

"A frown turns into a little of a softening of the face. That is just beautiful, and I really praise God for that." But there is no trace of self-satisfaction in Mr Street. He insists that often his charges make the most progress when he has had little to say. "All I care is that he's finding hope and comfort. This is not me - I'm just a bystander."

The Volunteer: Apart from weddings, funerals, and the occasional school trip, Andy Simpson had never set foot in a church until 2011. But, two years after a breakdown forced him to stop working as a lorry driver, his marriage failed, and his wife left him. "The world fell apart," he said.

He walked to the A13, a huge dual-carriageway road that bisects the East End of London and began to walk across it, never intending to make the other side. "The wing mirror of a lorry missed me by inches," he remembered. Somehow, he stumbled to the other side, his suicide bid foiled.

For reasons he still can't quite explain he found himself driving to a church near by. The vicar, noticing that Mr Simpson was penniless (he had given all his money to his wife), sent him to a local foodbank, which was run by LCM.

"They were very friendly and kind people," he said of the volunteers and missionaries he met there. "They were prepared to give everything and want nothing back. It was like an atom bomb going off."

After a few weeks, he began helping out with the washing-up, and was eventually taken on as a volunteer. Seeing the changes in him, his wife took him back, and later he became a Christian. As he recounted the story last week, he grappled for the words to describe the transformation in his life.

"I've found out what was missing in my life. There was a hole in my life, and every time I stuck a plaster over it, it fell off - a new car, or a new telly. . . I was probably a very selfish person, but everything now is about serving rather than taking."

He is effusive about the missionaries of LCM: "They are saints. . . helping people regardless of what the world throws at them. If there were [more] people like that who care for one another this world would be so much better."

Now, he's considering whether to go beyond "keeping the coffee hot" and start training to be a missionary himself. "The more I step up to the mark and do a little bit here and there, the more I love it," he said.

The CEO: Graham Miller, the chief executive of LCM, came to the organisation after nine years running mission work in Beijing. But he said that the two jobs weren't as different as they sounded.

"The thing that fascinated me was that, while I was running missionary work in Beijing, there was a real need for cross-cultural mission work in London," he said last week. LCM staff are expected to embed into their communities and learn how to speak about Christianity in the local culture just as foreign missionaries would.

"One of our values is courageous perseverance. Keeping going for a long time," Mr Miller said. "The work we are doing - for example, with the Bangladeshi community on the Isle of Dogs - it will take a lifetime."

Mr Miller also pointed to work among the cockneys of the East End: often it might take one person more than a decade to go from first joining an LCM-run football team to making a profession of faith.

Most days, his time is filled with steering through fairly radical change, though, rather than chatting with people or running football teams. He was brought in to turn around several years of decline at LCM, by boosting the number of missionaries it has, re-opening centres, and investing in training.

There are currently 71 missionaries with LCM, but Mr Miller aims at having 100 by 2018, and a further 20 young people on its restarted gap-year programme.

"We are basically doubling the number of boots on the ground," he said. "There are slightly uncomfortable moments but it's an exciting time. We are looking at where are the most spiritually needy areas - and making difficult decisions where necessary."

A slight note of frustration creeps in when Mr Miller talks about how LCM partners with other churches across the capital. "Our target is the bottom 20 per cent - about two million in the neediest parts of London. If you look at where the growing churches are, almost none of them will be in those areas. We don't want to be criticising but encouraging them that the mission field is still there."

Before a day of celebrations to mark LCM's 180th anniversary, Mr Miller said that he was acutely aware of what and who had gone before him at the Mission. Before he even took the job, he read a biography of LCM's founder, a young Scotsman, David Nasmith.

Knowing the history was something that was both valued and unavoidable at LCM, he said. At one recent event, he stumbled across a supporter who was 91-years-old - he had first met an LCM missionary 76 years ago, aged just 15.

As for the next 180 years, Mr Miller is convinced LCM will continue. He said: "I would love it if the Church did the work we do, reaching out to the least-reached and marginalised, [but] I imagine there will always be a need for LCM to help the Church."