Kam said she used "Carbon Dating" to determine the age of the cuts in the tree. Carbon dating is usually not accurate to more than 50 years and dating of objects grown since the start of nuclear testing are unreliable due to the change in background radiation levels.
After 20 years, the tree would have grown so much that the early notches in the bark would have grown over.
There are 20 notches on the tree, the last made two days ago, but Barnaby tells Winter to look back 20 years ago. It should be 19 years ago. (1 notch = 0 years, 2 notches = 1 year, etc.)
At about the 37:35 mark, the team mascots are play-fighting one another against a placard showing both teams and their color: Sharks/blue vs Panthers/red. Just a few seconds later, the cheerleaders, dressed in blue, which is the "Sharks" team colors, but, they cheer for the "Panthers," whose team colors are red.
Being a Sergeant, Jamie would not call Jones, who is a DI, by his surname. He would call Jones 'Sir' when he found out that Jones held a higher Officer rank.
When Jones is tied to the front of the tractor, the rope is simply looped around the prongs of the machinery. Even with the upward angle, he is tall enough and there is enough slack in the rope for him to have easily walked forward, pulling the rope over and off the prongs, and escaped.
Observant Jones never noticed that his landlady's favorite cricket bat was missing off the wall in the house they shared.