THAMES GUARDIAN - Photo taken Thursday 9th May 2013
For the Thames a new vessel was built by Alnmeritec and delivered in 2011. THAMES GUARDIAN is a stretched version of the Wave Guardian catamaran similar to that of the new Port of London Authority harbour patrol services launches.
I am assuming that she replaces an older vessel of the same name (photo here) and works alongside a far more frequent Environment Agency vessel THAMES CHAMPION.
More information on Briggs and the THAMES GUARDIAN at briggs marine