Having rewatched all #LineofDuty episodes from season 6 today, here are my 4 theories of who/what ‘H’ may be;

#Theory1
‘H’ may not be a person, but rather a place i.e. The Hill - a lot of ‘bent coppers’ are from there.

#Theory2
Lakewell said “look towards the Race Claim”
Race Claim with a ‘H’ is an anagram of Carmichael.

#Theory3
From earlier seasons, I’ve always thought that Kate is very suspicious in how she presents herself. She could be ‘H’.

#Theory4
Could be a plot twist and it turns out ‘H’ has always been Hastings.

OR

This thread could be wrong in its entirety and ‘H’ is someone else or some place else, in that case sorry in advance