A 64-year-old woman has become the first person to be convicted for her involvement in the wave of protests at fuel sites staged by activist group Just Stop Oil.

Catherine Maclean was charged with aggravated trespass after an incident at an oil terminal in Thurrock last Wednesday.

Maclean, of Hurstpierpoint, Hassocks, in West Sussex, was ordered to pay £409 in fines and costs after admitting the offence at Chelmsford Magistrates’ Court on Saturday, Essex Police said.

Just Stop Oil have launched a series of blockades of fuel terminals in southeast England and the Midlands since April 1 in a bid to force the Government to cut reliance on the fossil fuel.

The protests in Essex on April 13 focused on the Purfleet Oil Terminal, the Inter Terminal in Grays and the Navigator Terminal in Thurrock.

The group said they hoped the blockades would “significantly impact fuel availability at petrol pumps across the South East”.

Assistant Chief Constable Rachel Nolan said: “Sadly, Ms Maclean’s actions means she now has a criminal record.

“No-one – least of all my officers – wants to see this happen but it is a timely reminder that if you come to Essex to engage in trespass, even though you may see it as protest, you will be arrested, you will be charged and that is likely to lead to a criminal conviction.

“We are not anti-protest in any way. Individuals have a protected right to protest but these incidents have unfortunately crossed into criminality and we have been left with no other option but to act and seek authorisation from the Crown Prosecution Service to charge people.”

Two other activists – James Skeet, 34, of Drayton Street, Manchester, and Stephanie Aylett, 27, of High Oaks, St Albans – appeared alongside Maclean at Saturday’s hearing.

Both denied a charge of aggravated trespass and breach of bail conditions, Essex Police said, and were remanded into custody and will appear back at Chelmsford Magistrates’ Court next week.

So far, 23 people have been charged in connection with the disruption around Thurrock since the beginning of April, Essex Police said, and it has made 461 arrests.

Meanwhile, the Metropolitan Police said they had made 213 arrests for a range of offences during the past week related to Extinction Rebellion protests across the capital.

The force tweeted: “Officers have worked hard over the past week to minimise disruption to London and its communities whilst various protests by Extinction Rebellion took place across London.

“We have made 213 arrests for a range of offences including public order and obstruction of the highway.”

The Met said 70 people were arrested on Saturday for offences in connection with disruption at Marble Arch during which the London landmark was scaled as a banner was hung in protest against the use of fossil fuels.