A trial would have been nice. Probably too much work though.
But the article clearly shows that you have to have the approval of a magistrate and that in this case there are going to be further hearings to decide whether to continue the order. Therefore this man will have plenty of opportunities to challenge the legitimacy of the order in court it's not purely arbitrary.
I looked up the criteria for Sexual Risk Orders. They are imposed:
"where a person has done an act of a sexual nature as a result of which there is reasonable cause to believe that it is necessary for such an order to be made, even if they have never been convicted. They replace the previous Risk of Sexual Harm Orders.
The court needs to be satisfied that the order is necessary for protecting the public, or any particular members of the public, from sexual harm from the defendant; or protecting children or vulnerable adults generally, or any particular children or vulnerable adults, from sexual harm from the defendant outside the United Kingdom.
A prohibition contained in a Sexual Risk Order has effect for a fixed period, specified in the order, of not less than 2 years, or until further order. The Order may specify different periods for different prohibitions."
So there are a number of safeguards built in.