It appears the priest John Assheton was the first person tried in England for anti-trinitarianism on this day in 1548.
From this distance it is hard to tell if he was a Socinian or an Arian. Probably his views conflated these perspectives, although he did seem to argue that Jesus was a human being and not some aspect of God. Archbishop Thomas Cranmer gave him the alternative of continuing to hold his view publicly and being burned at the stake or abjuring his heresy. The Reverend Assheton chose to renounce those of his views that differed from those of the Archbishop.
While Assheton avoided death, there would be a handful of people who would die for these views in the next few decades.
And the seeds of what would become Unitarianism nourished by martyr blood would begin to germinate…