The story's interest dwindles as far as the public are concerned, but the dogged team, led by Marina Litvinenko continue to look for answers. Eight years on, and a public enquiry is ordered.
This was the disappointment as far as the series was concerned, I thought that this fourth and final part was too slow, too padded and was just unnecessary.
This fourth part could have been so different, a shame Tennant didn't take on Litvinenko's earlier years, and give us some detail as to why he was targeted by The Russians, I came away from here feeling like I still knew very little a out him.
Excellent, we've found something positive that Theresa May did in her time as Prime Minister.
Margarita Levieva did a great job throughout, a very strong performance.
I can't help but feel disappointed with this conclusion.
5/10.