Becuase its a ring circuit as opposed to a radial one, there are two paths the current can flow down, in a fully loaded, but perfectly balenced ring there will be 16A on each section of 2.5mm², but because things arn't that simple in real life, in a ring circuit the cable should be rated to 2/3 of the overload protection, 2.5mm² T&E has a rating of 22A in the situation its likely to be installed in a house, rising to 27A in free air.
This is why broken rings are a bad thing™, especially if the break is towards one of the ends
This is why broken rings are a bad thing™, especially if the break is towards one of the ends