That was in a specifically protected area covered by a PSPO that explicitly banned prayer. He then refused to move on, so this was a deliberate protest against abortion.
> On the day, he was asked to leave the area by a community officer who spoke to him for an hour and 40 minutes - but he refused.
I don't think you've got a clear understanding of how PSPO orders work. Do you really think that standing and thinking would be a criminal offense? Maybe if you stood somewhere awkward (e.g. blocking the doors to an A&E department) and refused to move when asked, then I can understand it, but I think you're being disingenuous.
In the linked article, the criminal was not alleged to have obstructed anything. He did message the town council saying he was holding a silent vigil, which he had done before apparently without incident. This time he was arrested, PSPO was applied, and he was fined £9000.
If his message to the council
said he’d be standing there reading the newspaper, would the arrest and conviction have been made?
The PSPO specifically prohibited activity in favour or against abortion services, including protests, harassment and vigils. He was blatantly holding a vigil and even then, I expect he could have just moved on when asked and faced no charges. Reading a newspaper would be fine, obviously, unless he specifically concocted his own newspaper with slogans on it which would then surely be a protest of some kind.
> On the day, he was asked to leave the area by a community officer who spoke to him for an hour and 40 minutes - but he refused.
https://www.bbc.co.uk/news/articles/c4g9kp7r00vo