Sounds like you saw the Black Shuck ferg.....
“He takes the form of a huge black dog, and prowls along dark lanes and lonesome field footpaths, where, although his howling makes the hearer’s blood run cold, his footfalls make no sound… . But such an encounter might bring you the worst of luck: it is even said that to meet him is to be warned that your death will occur before the end of the year. So you will do well to shut your eyes if you hear him howling; shut them even if you are uncertain whether it is the dog fiend or the voice of the wind you hear… you may perhaps doubt his existence, and, like other learned folks, tell us that his story is nothing but the old Scandinavian myth of the black hound of Odin, brought to us by the Vikings… .”

And in addition to the above, perhaps the most distinctive characteristic of the Black Shuck was its eyes, red and big as saucers.

Furthermore, these hellhounds were always said to appear suddenly and without warning, then disappear as quickly as they’d arrived. And if you did catch a glimpse of one, it was believed to be either a protective spirit, according to Modern Farmer, or a portent of death — a family guardian watching over everyone or a warning of certain doom.
https://allthatsinteresting.com/black-shuck
thats just what they call it in Norfolk where Im from but its got a lot of other names depending where people spot it.