Boris Johnson is in Northern Ireland on a mission try to stop the government cutting London's transport budget.
The mayor is visiting the factory awarded the £200m contract to build a new double decker - the so-called Boris Bus.
City Hall claims the 600-bus order is creating 50 new jobs and is evidence of how investment in London benefits the wider UK.
The mayor and his transport bosses are locked in a battle with the Treasury ahead of next month's spending review .
TfL says it needs £1.8bn a year from 2015 to upgrade the Piccadilly and Bakerloo Lines, carry out road improvements and deliver a radical cycling plan for the capital.