Here is the series if anyone missed it.
Part 1.
YouTube - Ross Kemp In Search Of Pirates 1 (1/5)
Around 4:45min is when Ross joins HMS Northumberland...
He then patrols with the Merlin crew.
Part 2.
YouTube - Ross Kemp In Search Of Pirates 1 (2/5)
Continued onboard Northumberland
You can click on the rest on the right hand side of Youtube.