It commenced on 11 December 2021 as a joint venture between RATP Dev and Kelsian Group.

In December 2024, RATP Dev agreed terms with FirstGroup to sell the business.

In September 2021, RATP Dev and Kelsian Group agreed to form a joint venture to combine some of their Transport for London contracted bus operations.

RATP Dev Transit London commenced with 1,250 buses on 115 routes from 10 garages.

RATP's London operations have been impacted by a bus driver shortage, inflation and strike action resulting in a 10% pay increase compared to the initial 2.3% offered.