Time and time again we hear complaints about Royal Mail's apparent inability to deliver stuff to Capita. It suits Capita to let them take the flack and masks their lack of organisation. On a personal basis I use Royal Mail to send parcels, large letters all over the UK and in the last 10 years they've only failed twice. I don't pay extra money for "signed for" or "First Class" or even registered. They pay compensation if it's lost second class as long as you get a proof of posting(which is free on request at the Post Office).
Royal Mail are far from perfect and given that they deliver to every address throughout the UK without fear or favour there is going to be the occasional slip up but certainly not as often as Capita are wanting us all to believe.
Readers of Private Eye magazine will know that Capita have a nick name gained from their poor reputation in other fields which involves inserting an "r" between the capital C and the first a.