Please don't take this as Devil's advocate but just for balance until more detail comes out.
Breach of the peace, along with contempt of court/perjury has occasionally seemed disproportionate in its sentencing to me. For example in speeding cases where a camera has photographed a number plate from behind and the perpetrator thinks he/she may not be identified easily there have been examples of (typically) a wife taking "points" that should have gone against her husband because he was driving the car. He may have - say 9 points - and if he gets another three then he will get banned.
Do this, get caught and you will go to prison. So an offence which of itself would amount to a £100 fine ends up with three months in prison.
So ... Tommy Robinson. I understand where he comes from completely ... but ... like many "crusaders" you can go too far. As I see it he had an accumulation of offences which meant the "slammer" for him. 13 months seems disproportionate but if he is a good boy he will be out after six and a half and as a "known" face he is unlikely to be killed/injured in prison.
As for the case he is protesting about - there is a very real danger that (if he "skews" the case by highlighting details or inciting a view that defendants are already guilty) there is a very real chance that the defence will cry "foul" and there will be a mistrial and they might get off scot-free.
He was jailed for contempt of court for three months last year, suspended for eighteen according to The Independent. And so a second offence can automatically trigger being sent to prison.
https://www.independent.co.uk/topic/tommy-robinson
"Don't jump to conclusions too soon" has been my motto since dealing with JW-ism and it holds good for now. Watch this space.