Armed officers, including England's most highly trained police marksmen, swooped on a traveller site in a raid targeting suspected organised crime.
The incident in south east London earlier this morning followed months of work by police gathering sufficient evidence.
So far six people have been arrested over offences related to drugs, stolen goods and burglary.
Officers used distraction techniques before they raided the site in Star Lane, Orpington, while drones were also spotted above the site.
The raid, involving hundreds of officers, is one of the biggest armed operations run by the Metropolitan Police this year.
It included counter terrorism specialist firearms officers, who train with the military, although there is no suspected link to terrorism.
Two people found at the site are being cared for by the force's modern slavery team, and 17 dogs have been seized.
Commander Kyle Gordon, the gold commander for the operation, said: "Tackling violent crime remains the Met's top priority and our efforts to prevent serious harm and loss of life on the streets of London have not wavered, including over the last few challenging months.
"This operation clearly demonstrates that every officer - from local neighbourhood teams all the way up to our specialist crime investigators - is focused on bringing those responsible for violence and organised criminality on the streets of London to justice, to keep our communities safe.
"Over recent months, we have seen an increase in the number of firearms incidents across London and proactive operations like this are crucial to removing the availability of weapons and drugs on the streets.
"We have now seized dozens of lethal firearms and prevented them entering the hands of dangerous individuals."
Investigators will now spend around two days searching the 22-pitch site, following intelligence about where guns might be hidden.
Superintendent Andy Brittain said the force is working with the local council to accommodate residents including children while the searches are carried out.
