So just how worried are we?

Thursday January 10, Islington, north London

As well as recces, there is a pile of other preparations to make: visas and hotels, pinning down access to places and finding contributors, arranging insurance and equipment, pulling in other members of the production team. At present we are planning to film in the UK, USA, France, Spain, Italy, Poland, Hungary, Turkey, Russia, Egypt, Tunisia, Israel, Syria, Iran, India and Singapore, all before Easter.

We negotiated access to most of our sacred sites before Christmas, but there are one or two late choices still to pin down and inevitably problems come up with one or two of those that we thought were fine. St Basil's Cathedral on Red Square in Moscow begins to look flakey because, our local fixer explains, of the forthcoming elections in Russia. And then we run into difficulties for filming at the Chapel of our Lady of Rosary in Vence.

We hoped to finish the Christianity film at the exquisite chapel designed and decorated by Henri Matisse for a house of Dominican sisters near Nice. The convent itself is welcoming and the Matisse estate give permission but it proves impossible to work out an appropriate and affordable arrangement for rights and permissions with DACS, the copyright society that collects reproduction fees for artists.

To date, losing the Matisse chapel is our only disappointment in the planned schedule. Even so, the logistics at this stage feel a touch overwhelming. To better prepare ourselves, we watch together some films that have touched on this territory before. There can be something quite consoling about a collective viewing of someone else's documentary about the subject you're working on, especially if it was made a few years ago. Apart from anything else, you can make a note of the spectacular shots which work and promise yourself and your colleagues that you can do better than the rest of what's on the screen.

We look at parts of the series "Heaven on Earth", six half-hour programmes made with the presenter Christy Kenneally by Tile Films in 2003 and at Wag TV's "Divine Designs" series with Cambridge academic Paul Binski. Both series visit two or three of our sites, although they treat them far more as places of architectural interest than as contexts for religious belief today.

Another reference point is the recent David Dimbleby series "How We Built Britain". Among the things we take from this is that a seemingly limitless budget for helicopter shots in a wondrous thing and that buildings look a hundred times better in sunlight framed against a blue sky dotted with white clouds. We of course are filming not at the height of summer in most of countries but in the winter months with a light that will be pale, grey and even. One more thing to worry about. (John Wyver)