A court order is being sought to move a group of travellers with more than a dozen caravans and vehicles on from a park.
Harrow Borough Council is taking action against the travellers and their vehicles after they illegally entered and occupied part of Queensbury Park, in Honeypot Lane.
The council is set to seek a court order to have the vehicles removed, and police were at the park last night to monitor the situation.
Council leader Cllr Susan Hall, who visited the site yesterday, said: "In just the space of a few hours there's already been damage to the grass from cars and caravans driving around the park, as well as littering and fly-tipping.
"These people have no right to simply set up home anywhere they like.
"This is nothing to do with ethnicity or lifestyle choice; the fact is being a traveller does not mean you can take a pick and mix approach to the law, you have to abide by the same laws about where you can live as everyone else does.
"It has been made clear to the travellers that they are there illegally and need to move on, but we will be seeking a court order in case they do not."
In January this year travellers set up camp in Chandos Recreation Ground, in Camrose Avenue, Edgware, and were moved on after a court notice was issued.
Last year police moved on an encampment of 20 caravans on the site of the Kodak Sports Ground in Harrow View.