Just to clear up all the exitement it was Bittern, just she is running in blue as 4492 -Dominion of New Zealand at the moment - I think its all to do with charity relief for the earthquake or something.
Thanks for that 07, had it confirmed to me by an enthusiast, apparently due to stay in blue livery until the end of 2012 when its future is a bit up in the air as the boiler ticket will run out then.