I don't know how to attach a pdf but if you click on this link
https://www.google.com.au/?gws_rd=ss...=1496382161165 the third one down is The Story of Helmets Integrated Systems Ltd.
It's a 32 page booklet about Helmets Ltd., Wheathampsted 1924-1984. Hopefully it'll be of some help.
This site says they designed the MKI liner in 1936
http://nuke.combat-helmets.com/World...9/Default.aspx
Tony