Watch our report from Simon Harris above.
The Routemaster is the first open-platform bus on London's streets since the old buses were withdrawn from service in December 2005.
Championed by London Mayor Boris Johnson, the bus is the first of eight new Routemasters that will run along route 38, which runs between Victoria station and Hackney.
When he was elected Mayor in 2008, Mr Johnson promised a return for a new green successor, as well as vowing to get rid of the ultra-long bendy buses, which have now all been withdrawn.
The Routemaster ran into problems on it's first public journey. The bus stalled halfway through the route in Islington, causing it run over 30 minutes late. Eventually engineers were called to reboot the entire software system.
it was just one of many issues reported with the new bus.
- The doors won't shut
- The weight of passengers caused the rear brake to stick
- A fault meant an audible alarm could be heard throughout the journey.
Boris Johnson says the problems will be fixed.
The Mayor of London said:
"We were always conscious that there were going to be teething problems, there's been a small software issue, it's now been rectified and you know doubtless there will be other teething problems, but it is a great new bus for London."
"It's what the city needs, it restores the hop on, hop off platform and I really think anybody who wants to replace this with the bendy bus and take this new bus off our streets needs their head examined."
Disability rights activists say they are disappointed at the design of the Routemaster.
Commenting on the New Bus for London, Lianna Etkind from Transport for all said:
"The New Bus for London is a missed opportunity for a bus that works for all Londoners, including wheelchair and pushchair users."
"Bus drivers’ guidance is clear: wheelchair users take priority over pushchairs in the wheelchair bay."
"But the reality is that when the bay is already occupied by a buggy, drivers are often reluctant to ask parents to fold their buggy away, and when there is a conflict over the bay, all too often wheelchair users are left behind on the pavement."
23 year old Tamisha Archibald, who uses a wheelchair, wanted to be one the first passengers to use the new London Routemaster but she was unable to board and it left her behind.
"I find trying to use public transport in the capital is frustrating. Usually if I have an important meeting, I have to do a test run the day before to see what hurdles I'm going to face when travelling the next day. The old Routemaster was very narrow, which meant getting space during busy periods was very difficult."
"I arrived at Victoria bus station where my frustrations are already clear to see.
The stop has very narrow paths, which are obscured by bollards. This meant I had to go to the other side of the station to gain access to where the new Routemaster will stop. I was left behind when they stopped as the driver did not notice me trying to get on the bus."
Transport for London say the buses are accessible.