Slate 100, our first today, is often the occasion for a little on-set celebration, sometimes with bubbly. Not, however, on our tight schedule for Macbeth, where it passes with only a doodle on the clapperboard and a modest cheer when it's first called. There are times on a shoot when you need to pinch yourself. Is this all a dream? We've walked several hundred yards along a broad dark tunnel built with  immaculate brickwork. We've ducked through an archway into a kind of cloister with brick vaults around a central space over which a ruined iron and glass canopy hangs. Fallen panes lie cracked and broken in a carpet of leaves and a twisted mass of metal rails is tangled up in tree branches which have grown through them during the past decades.

This is an eerie lost world, a nineteenth century pleasure garden that crumbled and rotted through the twentieth, and that today is a perfect location where no-one has filmed before and relatively few people have even seen. By 9.30am there are forty cast and crew here, preparing a final assault on Dunsinane. We have soldiers in camouflage webbing and principals toting AK-47s. Our two cameras catch them creeping around the setting, preparing for battle and being fortified by Michael Feast's Macduff urgent cry of 'Blood and death'.

We're confined by the (appropriate) strictures of health and safety rules to the spaces around the central area. It's just as well that no-one defies the ban and creeps out under the canopy since at least twice we notice elements of the glass come lose and fall. It's a long morning but a fruitful one, securing shots that ought to suggest a convincing sense of conflict.

For each set-up, not only do the lamps have to be in the right place (and getting the generator close enough to here has not been a trivial task) but there are also the logistics of moving around the cast and the supplementary artists or SAs (who once were known as extras). Costume and make-up crew need to be on hand to check their contributions before each shot, and the latter have all-important sweat to apply frequently.

Just outside the camera frame water is being sprayed across the lens while dust is shaken to fall through the shot. Muffled explosions on the soundtrack (to be added in post-production, of course) will suggest this debris is caused by shells falling nearby. Disconcertingly a camera assistant is shining a small torch straight at the lens of each camera as we record. This flares across the recorded image, heightening the overall sense of confusion and chaos.

Forty people or more focus through the morning on achieving all of this, a group of highly skilled professionals working at the top of their game to make something really quite special for the screen. But at the same time it's occasionally hard to resist the sense that this is a bunch of kids playing at being soldiers.

By mid-morning we're all a bit cold and damp, and I have to reassure our make-up designer Deanne Turner that this is only the second most miserable filming location for the production. But it's beaten in the discomfort stakes by where we end up after lunch, which a space deep below ground that we call the sewer. It's actually part of the access area to this location's heating system, but it's wet and confined and airless altogether difficult. And it becomes even more so when we have to fire a gun down there, which despite ear protectors is still extraordinarily loud.

The armourers have further work to do towards the end of the day, when we have to execute the Thane of Cawdor. This is a scene that Shakespeare has Malcolm report: '...nothing in his life / Became him like the leaving it'. We have him executed on screen, shot through the head with his brains and blood spattered on a wall. We rig a hidden compressor that fires a blood capsule -- and the final result on the monitor is eerily impressive. But we also record the shot without the blood in case the image proves too strong for television in one or more of the territories where the final film is to be screened.

After the murders yesterday and the killing today, by the end of the filming, at two minutes past seven, everyone's ready for a rest day tomorrow. Incidentally I am also contributing to the blog at Great Performances, and you can access my first contribution here.