Sea Brown Trout (surely?) over a metre long in the River Little Ouse upstream of Brandon

As I was going down the Little Ouse, a chalk stream forming the border between Norfolk and Suffolk, I saw a big fish move under a fallen tree. On my way back up I approached stealthily and nearly choked when I found probably the biggest fish I've ever seen in an East Anglian chalk stream, even bigger than any Pike. Surely it is a Sea Brown Trout (Salmo trutta ssp. trutta)? It was over a metre long - and sure enough, if you look at a photo of the fish with a minnow in breeding colours right next to it, assuming minnows are 6 cm, then the fish is 104 cm. It seemed much bigger than all the other large Brown Trout I have encountered, such as this one https://x.com/numenini/status/180746448897.... With a much longer, more torpedo like shape (rather Pike-like), no trace of red on its adipose fin, and the spots on its flanks are unlike any I’ve seen on Brown Trout – more star like than the usual round, black or red ones with white trims, and the absence of spots on its tail seem to differ from Brown Trout, though it does have spots on its dorsal fin. Also, I wouldn’t have said it is particularly silvery so maybe it has been out of the sea for a while. If it is indeed a Sea Trout then it could be the first recorded in the Little Ouse in recent times and is an indicator of the success of river restoration activities including the installation of fish passes at Denver and Brandon. It seemed to be attracting a lot of attention from the other fish in the vicinity, seemingly playing grandmother's footsteps with it - especially the minnows and sizeable Perch but also a few Gudgeon - suggesting it wasn't a resident. GX011885 4 3 Sea Trout minnows perch swans gudgeon 4K