How prevalent is noise-induced hearing loss with UK troops?

More than 2/3 of British troops returning from Afghanistan suffer from severe NIHL.

Answer Extra: 

In a study released by the Deafness Research Foundation and the UK Ministry of Defence, nearly 69% of UK troops returning from Afghanistan had suffered hearing loss due to combat noise. Many combat troops complained of tinnitus, some of complete deafness.

source: 
Pearson, Chris (Surg. Cdr., RN). “The Extent of Operational NIHL.” http://www.deafnessresearch.org.uk/docs/research/mod/SurgCdrPearson.pdf