a) Tell the story of Christ's Passion, his suffering and crucifixion, in a way that's fresh and universal.

And

b) Set it in Preston.

That's it.

Writing drama for TV normally means having a detailed series outline to stick to, or piles of research to trawl through, or a novel to adapt.

But this?

A blank page is always daunting, but this was so blank. Where do you start?

By ripping up the rule book, and going to Preston.

My writing partner Lyall Watson and I spent six months in Preston talking to local people - faith groups, museum curators, leaders of the immigrant communities, prison visitors and people who came forward generously to share their stories: recovering alcoholics, war veterans, victims of crime and racial abuse and perhaps most affecting - a group of young carers.

All shared stories with us of quiet, personal heroism and sacrifice.

For me this research process was extraordinarily moving and a completely new way of developing television drama.

From the ground up. By listening.

Aaqil and Hilary Martin, the executive producer, wanted the drama to be 'universal'.

It must speak to people of other faiths and no faith as well as to Christians.

By telling very human, personal stories we hoped to avoid falling into the trap of re-enactment.

We wanted enactment, to make the Passion dramatically REAL and close. The story of the Cross as it matters everywhere and at all times, not just in Jerusalem 2,000 years ago.

Bishop Crowther (Ronald Pickup) and Samuel Horrocks (Tom Ellis) in Pilate

And we settled on a formula: a passion story must have at its heart an act of gratuitous self-giving love that somehow turns the world upside down.

No longer blank the page is now a scrawl of notes for many stories.

It's at this point we decide to write not one Passion, but three: to tell the familiar story from three different points of view - Pilate's, Mary's and Jesus'.

So Pilate's story is mirrored for us in the story of Sam Horrocks, the mayor of Preston in 1842.

Confronted by a town in turmoil during a mill workers' strike he must decide between the starving workers on the one hand, and the powerful mill owners on the other.

Like Caiaphas in the gospel, the Church of England sides with the mill owners and the strike leader's fate is sealed.

Our connection with Mary, the mother of Jesus, is through one of the many women who ran a free cafe on Preston railway station for the troops during World War I.

She bravely continues to serve while awaiting news of her soldier son.

And the self-sacrifice of Jesus is reflected here and now by a 12-year-old girl.

The daughter of an alcoholic mother, Bella cares for her young brother and sister.

As she shops, cooks, baths and loves them she passes through the traditional Stations of the Cross (the stages in Christ's journey to his death).

It's a way of telling the Passion story that satisfies me as a committed Anglican, and Lyall, an agnostic.

Did we ever argue about religion? Of course. But then having written together for years we argue about everything.

And most importantly we both feel enriched by our encounter with the Passion and with the people we met in Preston.

The Preston Passion has been a turning point for both of us - a reminder of why we wanted to write in the first place - to share stories. To share.

Colin Heber-Percy is the co-writer of the three short dramas which form part of The Preston Passion.

Comments made by writers on the BBC TV blog are their own opinions and not necessarily those of the BBC.