[2] A network of Green Line limited stop orbital routes was established by the London Transport Executive from 1953.

[4] The 2008 mayoral election manifesto of Boris Johnson promised to trial orbital express bus routes in the outer suburbs.

[6] The policy had been abandoned by Johnson by March 2010, citing "plenty of good studies now which suggest to me that the big investment in orbital bus routes does not actually deliver the improvements that are sometimes claimed" and there was no further expansion of the orbital network.

[13] The Superloop branded proposal for a network of express orbital bus routes was announced on 28 March 2023 at a cost of £6 million.

[16] The proposal was praised by the Campaign for Better Transport and Heathrow Airport Holdings,[16] however Nick Rogers AM of the Conservative Party called the proposal a "superflop" drawing attention to the "repacking of existing [bus] routes".

[16] Caroline Pidgeon AM of the Liberal Democrats cautiously welcomed the proposals, following her previous campaigns for orbital bus services.

[27] In March 2024, the loop was completed, with route SL4 to be introduced when the Silvertown Tunnel opens on 7 April 2025.