E.T.R.T.O. 1991 - Section 13 - Caravans & Trailers:
An increase of 10% over the load capacity quoted in the tables is permitted when tyres are fitted to caravans and light trailers with a maximum operating speed up to 100 km/h. (60 m.p.h.). The basic inflation pressure should be increased by 3 p.s.i. / 0.2 bar.

This 10% bonus loading is widely used in the U.K. light trailer industry, but should only be used on trailers that are to be sold within the U.K. The caravan industry in the U.K. tends to ignore this bonus loading and use loadings at 130 km/h / 81 m.p.h.