How Fast is the ULTIMATE WiFi Internet package on P&Os Britannia?

As a social media manager for a sports club I needed internet on my recent cruise in the Caribbean. I couldn't find any information on expected speeds so I hope the info helps you to make a decision. There are two packages currently - ESSENTIAL and ULTIMATE. This info is for the higher priced ULTIMATE package.
Although there were some dropouts, internet was available, at different speeds, for 99% of the time I needed it.
*You can always access free WiFi at each port the ship attends to keep up-to-date!
I'm not an IT tech, so please bear this in mind. You may get much better speeds with better equipment etc.