Casdon
www.dailypost.co.uk/news/local-news/what-cattle-farmers-should-know-8964531
It is illegal to have an adult bull in a field with a footpath because of the risk to the public on a right of way. There’s info on the Rambling Association site about what to do if you know this is happening.
It's not illegal, Casdon, it's what Blossoming said.
From your link:
Section 59 of the Wildlife and Countryside Act 1981 bans bulls of recognised dairy breeds (eg Ayrshire, Friesian, Holstein, Dairy Shorthorn, Guernsey, Jersey and Kerry) in all circumstances from being at large in fields crossed by public rights of way.
Bulls of all other breeds are also banned from such fields unless accompanied by cows or heifers, but there are no specific prohibitions on other cattle. “Fields” in this legislation do not include areas such as open fell or moorland.
I must admit I'd be dubious about a field with cows and a a bull in it, whatever its breed...