I took a call last week from a gentleman who wanted his 50" LCD screen hung on a chimney breast. Normally this is a very simple job, in fact installing LCD TVs is one of our most common tasks. But in this case the customer had a cantilever style bracket and he lived in Clapham. Both of these facts set alarm bells ringing.
The cantilever style brackets undergo allot more bending and twisting forces than a flat or tilting bracket would ever have to deal with. These forces are transferred to the wall and fixings. Therefore to hang an LCD TV of that size on the bracket he had there would have to be no doubt to the structural integrity of the walls.
It is however our experience of many years of hanging pictures, LCDs and curtain rails that it is often the case that the old brick that holds up our homes simply crumble away when drilled into. This is particularly true for houses in the Clapham area of London and was the case with this customers chimney breast.