How do the two sets of This Morning windows differ out of interest? I remember the Albert Dock having a distinct dark patch where the studio was and shots from outside the studio at LWT give the impression that they are metal panels from the outside. How do these compare to the technologies being suggested for Daybreak?
The traditional way to darken down windows is by using either a neutral density filter or a scrim.
Neutral density is like any other type of colour filter (usually used over lighting), but as the "neutral" suggests it is without colour - or rather, it filters the whole spectrum evenly, so that it reduces the overall light levels, without altering the colour - so blue sky still looks blue, green leaves remain green and so on. ND filter (as its commonly known), works on an "additive colour" basis, meaning you can add many layers of light tint to result in a deep tint. This is useful for variable light conditions, so you can adjust accordingly, and often they are mounted on rollers (much like a roller blind), so you can add and remove at will.
A scrim is usually made from a black vinyl material perforated with thousands of tiny holes. Similarly this will reduce the light levels - but if seen on camera, can cause a stroboscopic effect. Therefore it is primarily used where it is not in shot.
The This Morning windows would have likely had the former treatment on them.
Polarising filter is more expensive, and utilises both an acrylic or flexible material over the window, as well as an optical glass filter on the camera lenses. It will reduce the light in the studio by around one stop - but from the camera perspective you can make the window appear (almost) black, if required, and anywhere on the scale in between.
Here's a video showing the application of both polarising filter and the neutral density solutions by Rosco - an American manufacturer.
http://www.youtube.com/watch?v=GrTlOosJRrI