PARIS, FRANCE -- After two months of trekking across France, a French-British duo have completed their campaign to stop mask litter during the coronavirus crisis, having picked up every discarded face covering they spotted while walking to Paris from the Mediterranean city of Marseille.

Edmund Platt, a British environmental activist, and his French friend Frederic Munsch set off on October 1 to follow the high-speed TGV train line to the French capital, aiming to open people's eyes to the extent of everyday pollution.

"We ended up with 6,300 masks," Platt told AFP in Paris, speaking French with barely a trace of accent after living in the country for years.

The pair walked 880 kilometres in total, a French and British flag on their backs, camping out or invited to stay in people's homes as they skewered mask after mask on long sticks.

They also carried sacks to pick up other trash including fast-food containers, newspapers and even a licence plate.

A series of media interviews made them mini-celebrities along the way, easily visible in their fluorescent orange safety vests as they showed off their daily haul.

"All these masks are from just a few kilometres, we've got 250," Munsch told a resident peering from her first-floor window in Melun, just south of Paris, a few days before the pair arrived in the capital on Saturday.

One a day

"What we'd like people to do is just to slow down a little bit and stop throwing away so much stuff," said Platt, who fashions himself as "The English Snail."

As part of their campaign they teamed up with an anonymous street artist based in Nice known as "Toolate" to advertise their work with framed portraits of masks that were hung above letter boxes across Paris.

"Here is the work of a jackass -- blue surgical mask thrown on the ground, dimensions 16 centimetres by 7 centimetres. Artist: Unknown," reads the sign above one picture in the trendy Marais district.

"It's a mask we found in a sewer grate, there was only the broken loop sticking out but I said, Damn, that one is for me!," Platt explained.

Having founded the @1pieceofrubbish movement several years ago, he saw the millions of disposable masks used since the start of the COVID-19 pandemic as a way to give fresh impetus to his campaign.

"The goal now is to get everybody involved, everybody picking up one piece of trash a day," he said.

On Friday, Platt and Munsch will host a "garbage-aperitif" -- a litter pick-up with drinks -- outside Paris City Hall, which they hope will include an appearance by Mayor Anne Hidalgo, who has made cleaning up the capital a priority.