He is a longstanding loyal Gove adviser who returned to government in June 2017 when Gove took up his latest ministerial role in June 2017, after spending six months working for Portland Communications. During his time at the Ministry of Justice Cook also spent three months as co-convener with Gove on Vote Leave. 
Cook worked under Gove in the Department for Education, but resigned when Nicky Morgan was made education secretary in the 2014 cabinet reshuffle. He has also worked as a SpAd for the then deputy chief whip Alistair Carmichael.
- MWW The UK Government July 2015, accessed 15 July 2015.
- Henry Cook, LinkedIn, accessed 25 August 2017
- Christopher Hope Nicky Morgan clears out Michael Gove's reforming policy advisers Telegraph, 21 July 2014, accessed 4 June 2015.
- Special advisers in post, 30 November 2014 GOV.UK, accessed 1 May 2015