Derek James meets photographer David White who has been recording the lives of churches in the 21st century.

More than 50 medieval churches once stood within the city walls. Today just nine hold regular parish services.

Here, people still gather on Sunday mornings to sing and pray and preach; and here, for the past 15 months, photographer David White has been recording the 21st century lives of these remarkable old churches.

David has worked as a scientist for most of his career. He taught at York University and was director of science for the national council which funds academic research and training before becoming director of the Institute of Food Research, in Norwich.

Then, in April 2009, at the age of 67, he changed direction completely. 'I never use the word retire!' he said. Instead, he began working as a full-time photographer.

He had loved photography as a teenager, but then confined his photography to holiday snaps for years. However, he had long been an expert on the science of sight and colour.

Today he specialises in portrait, documentary and wildlife photography and his latest project began when he photographed the Rev Hereward Cooke, the much-loved Norwich priest and politician who died suddenly in 2009 after cycling to the Copenhagen climate change conference.

David's portrait of the priest in his parish church led him to wonder whether it would be possible to photograph church services.

'I simply love the medieval churches,' said David. 'There have been a lot of photographs of the churches as buildings, but very few of the churches as people, and churches are, of course, as much to do with the people worshipping there as the buildings.'

He had thought it might be difficult to get permission but each of the parish priests he approached welcomed him and his camera to several services.

'I stopped going to church when I was an undergraduate but I have always been very interested and sympathetic,' he said. There are portraits of priests and parishioners, religious rituals and informal gatherings. Most are captured within the ancient and beautiful buildings designed for the needs of Norwich Christians many centuries ago.

Now an exhibition at Norwich Cathedral, and a book, have grown out of the project.

The Rt Rev Graham James, Bishop of Norwich, said he was delighted that David had documented the lives of city centre churches which are still loved and used for their original purpose. 'He shows that these buildings are at their best when inhabited by people engaged in prayer and praise, listening to the preaching of God's word and celebrating the sacraments,' said Bishop Graham.

One of David's favourite pictures shows children racing towards their Sunday School groups; some of the most difficult to take were in a church where incense obscured his subjects within minutes.

He said: 'Much as the churches express their devotion in such different ways, what stands out is that devotion, that commitment to a Christian way of life.'

In 2009 he was awarded a CBE for services to biology and his next project will link his old and new lives as scientist and photographer. He plans to photograph 101 British scientists for a book detailing their passion for science.

And the father-of-three, and grandfather-of-four, who lives with his wife in central Norwich, is passionate about his own new career. 'I'm having a whale of a time. It's fantastic,' he said.

The Living Medieval Parish Churches of Norwich, the exhibition of David's photographs of the nine churches, runs in the new Hostry at Norwich Cathedral until March 25. It is open from 9.30am to 4.30pm Monday to Saturday and 12pm to 3pm on Sunday.

The priests serving each of the nine congregations have introduced their church and the Bishop of Norwich has also written about the churches and the photographs.

A book of the project, also called The Living Medieval Parish Churches of Norwich is available from David's website at www.davidwhitephotography.co.uk