Older people who eat fish at least once a week could cut their risk of Alzheimer 's by more than half , a study suggests .
Researchers found that people 65 and older who had fish once a week had a 60 % lower risk of Alzheimer 's than those who never or rarely ate fish .
" We started our investigation of the child porn ring last year in August and soon realised that it was a big thing , " Mr Beer told a packed press conference .