Between 1961 and 1971 , Whitbread 's output increased from 2.1 to 7.4 million hectolitres .
Whitbread became Britain 's third - largest brewer by output .
Between 1961 and 1971 , Whitbread 's output increased from 2.1 to 7.4 million hectolitres and it became Britain 's third - largest brewer by output .