Producer Lisa Osborne on scheduling three directors at the same location on the same day.

Greenwich. Mid-August. Today is the day I have been dreading since we first put the schedule together at the beginning of March. All three Dorrit directors are on set today, each shooting an arrival at the Merdle house. Technically it's a block 3 day, so Diarmuid Lawrence is at the helm, but Dearbhla Walsh and Adam Smith are on set this afternoon to shoot a scene each and hysteria is rising as the hours until their arrival tick away.

The reason for the hysteria is spread on the ground around us where a crane is being assembled for the first shot of the day. It is 10.30am and Diarmuid is gazing at the constituent parts with an air of danger about him. It hasn't escaped anyone's notice, particularly Diarmuid's, that one crucial part of the apparatus - the track - is 30 miles away in Uxbridge. The clock is ticking faster than usual here in Greenwich and production manager Christine Healy is pacing up and down with her mobile clamped to her ear negotiating in a high-pitched whisper to get the rogue track delivered sooner than is humanly possible: “By river if need be!”

Spool back a year to a Little Dorrit pre-pre-production meeting. We have 14 scripts from the incomparable Andrew Davies; we have a budget, a draft schedule and a commission. What we do not have is a director and it has just become clear that if we are to air in October 2008 we will need not one but three like-minded souls to embrace Dickens' epic story, join hands with each other and with me and run hell for leather for the finishing line.

By the end of the year, two of the three have come aboard. Dearbhla is to lead and Adam will take the baton just as the first half of the story is about to come to the boil. His reward for drawing the second block is to take the Dorrit family to Venice, which we will create entirely within the M25. Thank God for strong-minded directors, though, because Adam will have no truck with this penny-pinching notion and spends a good part of his prep and shoot time arguing ferociously for a reduced crew to shoot at least some Venice for real. Which we duly do.

Dearbhla, Adam and Diarmuid have been generous collaborators with energy and enthusiasm for everything except our cat's-cradle schedule. We started filming on 28 April and Adam was on set for his first scene on 2 May. For two months he and Dearbhla danced a two-step through locations we couldn't afford to revisit until, at the beginning of July, a third partner joined the dance when Diarmuid stepped onto set and the two-step became a waltz. Which brings us to Greenwich in the middle of August and the one day when all three are on set together.

The day passes in a blur of crane assembly and concentrated activity and at 5pm sharp Diarmuid steps off set to make way for Dearbhla. In an hour she shoots the hell out of scene 5/01. But by 5.50pm there is no sign of Adam. James, the first assistant director, sidles up. “Do you want Diarmuid to direct [scene] 9/05?” he asks, but the words are scarcely out of his mouth when a silver Corsa whizzes through the gates and Adam arrives from the block 2 cutting room. At the camera Simon the script supervisor is giggling at how differently each director has handled their arrival scene - Dearbhla's is full of incident and character, Adam's bold and architectural, Diarmuid's has a storyteller's instinct for suspense.

Dusk falls. Dearbhla and Adam have left, the crane has been packed away and returned to base. Diarmuid has regained control of the camera. There is a Ferris wheel giving rides over the Naval College. Christine and I look at each other and slope off for a 10-minute breather. At the top of the cycle the wheel stops, time seems to stop with it, and we look down at the Little Dorrit crew beneath, calmly shooting the last scene of the day.

And now this article is late. It was due yesterday and it is late because yesterday was spent instead in a dub review for episode five with Dearbhla, choosing music with Adam for episodes six and seven and watching the latest cut of episode 14 with Diarmuid before it goes to the execs. Just the latest step in the Little Dorrit waltz.
l Little Dorrit was made by BBC drama productions for BBC1. Episodes seven and eight air on Wednesday 19 November and Thursday 20 November at 8pm on BBC1. A Little Dorrit omnibus airs on Sundays at 6.15pm on BBC1.

Lisa Osborne: My tricks of the trade

On a typical English summer the boot of the car is piled high with clothing for all conditions: fleece, waterproof, wellingtons and hiking boots, though even sunglasses are occasionally required.

This summer I never went far without my marked-up copy of Little Dorrit. Although obviously we were making the scripts, not the book, it's surprising how often cast and crew wanted to go back to Dickens for some tiny detail of character or description of a place.

A tin of Illy coffee. Can't start the day without a decent hit of caffeine!