Asbestos 
A mineral board containing asbestos fibres and generally supplied in plain or corrugated sheet form and other building items.
Also contained in some textured paints and ceiling decorative covering.
Although Asbestos has been banned since the early 1980’s care should be taken during
renovation works and if in doubt professional advice should be obtained.
http://www.hse.gov.uk/asbestos/surveys.htm