Activists from Dacorum and Tring Extinction Rebellion took part in a nationwide protest against Barclays Bank.
They were asking the bank to "clean up their act" by literally cleaning the Barclays branch in Berkhamsted High Street.
More than 300 activists from Extinction Rebellion entered over 20 branches of Barclays at midday on Saturday dressed as cleaners, before mopping up the public floor.
A spokesman said: "Since the 2016 Paris Agreement, 33 leading banks have lent $1.9 trillion to the fossil fuel industry, and this figure is rising year on year.
"Pouring money into the extraction of fossil fuels is destroying ecosystems, contributing to climate breakdown and harming indigenous communities, all of which undermine the future of life on earth."
They added: "Unlike most UK banks, Barclays are still willing to provide financial services for further Tar Sands exploitation and Arctic oil and gas exploration, the dirtiest of all the fossil fuels out there.
"These dirty investment policies directly threaten our future and our children's futures. By cleaning their branches for them, Extinction Rebellion hope to make it clear that Barclays must clean up their act before it’s too late."