The man who staged a protest on a bridge on the Devon and Cornwall border last week mounted another demonstration on a girder near the Blackwell Tunnel in London.
Fathers 4 Justice (F4J) named Jolly Stanesby, 35, a registered childminder from Ivy bridge, Devon, as the man on the gantry over the Blackwell Tunnel.
His action comes only days after he mounted a protest on a gantry over the Tamar Bridge, near Plymouth.
His latest protest brought rush hour traffic to a standstill on Monday morning.
F4J is a protest group which is calling for divorced fathers to be given greater access to their children.
Other members of the group forced the closure of the Clifton suspension bridge in Bristol on Monday, as well as climbing onto gantries on some of London's other key roads.
A spokesman for the group said that the protests were the beginning of a full-scale campaign of civil disruption.
A Scotland Yard spokeswoman confirmed on Monday that the Metropolitan Police's public order branch was policing a "number of demonstrations" across the city.