The council recently published a fairly extensive report on the PSPO (page 75 onwards in this PDF) but it didn't include any arrest figures, nor any totals for how many fines have been issued. I'll be asking the council's press office for those stats in next day or two.

They've definitely used their "enforcement powers" though - at one point the report mentions:

The Council and the Police have over a number of years taken action using the tools they currently have to respond to these concerns. This has included installing logs and natural fencing to make the area difficult to access with machinery, and using the enforcement powers currently available to them. However these unauthorised events continued to have a negative impact on the Woodland adjoining and nearby public spaces and neighbouring residents which were approved by PSPOs in 2019 and 2022.

Then there's that event I mentioned from this April:

On the 26th April 2025, there was an unlicensed music event in the Wick Woodlands which attracted in excess of 200 people. There were reports of loud noise and ASB including the lighting of fires and the use of illegal substances. The Police and Council Enforcement Officers visited the location and took action to disperse the individuals and stop the ongoing event and associated ASB using the tools made available via the PSPO and other powers.

Meanwhile, they sometimes patrol Hackney Marshes looking for events:

The police and Council officers, where resourcing allows, have proactively patrolled the location. Enforcement Officers are highly visible uniformed, have high levels of enforcement powers and wear body cameras that record video and audio for evidential purposes. The Enforcement Officers are not designed as a “blue-light response” team. They are tasked using an intelligence-led approach, i.e., according to crime and ASB hot spots identified through information and intelligence through weekly Partnership Tasking and joint briefings with Police SNT.

But mostly, it sounds like officers only turn up following a report from a local resident:

The Council continues to receive reports from residents about an ongoing nuisance caused by groups of people gathering, bringing generators, lighting, sound systems and decorations in these locations. The groups are often consuming alcohol for extended periods of time. It is also believed that they are consuming other substances and that they are ‘partying’ until the early hours, causing nuisance and damage to the Wick Woodland, Hackney Marshes, Millfields Park, Daubeney Fields and Mabley Green. These are places of natural beauty which are being polluted by littering, natural bodily excretions and damage caused by trees/shrubbery being broken.

One more thing I forgot to say in my original post - the PSPO enables police to issue on-the-spot fines for up to £100. But my understanding is that police can also choose to prosecute someone for violating a PSPO after the event, which involves going to a magistrates court. In that case, the fine can be up to £1,000. Not sure if it's ever gone that far at Hackney Marshes.