The big advantage of sitting Dame Judith in her private pew was that there was very little ambient light on her compared to the amount of light on the walls and windows of the Chapel. The problem of the private pew, however was that it is raised by about 1 metre (40 inches) from the level of the floor. Getting the flash up to the height required wasn't going to be easy and I had to make use of a rubberised cord to strap the shaft of the lightstand to one of the fixtures on the front of the pew. I used my own fleece jacket to protect the woodwork and managed to get the flash head, complete with it's umbrella box at about ten degrees above the subject's eyeline.
The ambient light reading on the beautiful woodwork away to the subject's left hand side was 1/8th of a second at f5.6 on 200 ISO. The task of balancing the flash with the ambient light is relatively easy because it is only the aperture that has a relation to the flash output. The physical act of changing the power output on the flash meant climbing out of the raised pew, walking around to the flash pack and changing the output before returning to the raised pew. Luckily I only had to make this tricky little trip twice and at 25 joules (25 watt/seconds) I had the correct setting. I had an 85b (full CT orange) filter over the flash and the camera set on the tungsten white balance.
The flash was at about 70 degrees from the axis of the lens and slightly above the subject's eyeline. This gave a slight pool of light with the light modifier and her feet weren't covered by the flash which added to this pleasant effect. The lens used was a 16-35mm f2.8 set at around the 20mm mark, which gave an interesting angle of view for this portrait.
Rather than rely 100% on the camera's excellent LCD screen to balance foreground and background I bracketed both the flash and ambient exposures to give a wide variation of exposures. I often do this if I am in the slightest doubt - a doubt that is often magnified if the success of the pictures relies on both elements being properly exposed. In this case I preferred the version where the subject was perfectly exposed and the ambient reading was nearly one f-stop overexposed. The wood in King's College Chapel is very old and very dark so a slight overexposure definitely gives a more pleasing result when reproduced on newsprint paper. Magazine reproduction gives you a lot more flexibility and allows you to be more subtle.
I had around half an hour shooting portraits around the inside of the chapel and used both wood and stained glass windows as backdrops. Shooting in amazing locations like this is always a great joy and when your subject wears a red suit it makes my job a lot easier!