(26 May 2021, 7:58 pm)IRHardy wrote Here is a link to the ULEZ website: https://tfl.gov.uk/modes/driving/ultra-l...ssion-zone which explains the requirements for vehicles in the ULEZ.

However all buses that operate on any TfL route now have to be Euro 6 or have been converted to be Euro 6 compatible (see this page on the TfL website: https://tfl.gov.uk/modes/buses/improving...tcmp=42923.)
so in answer to your question: "So are the Gemini1 Hybrids in London Euro5 then?"
No they are all now Euro 6 compatible.

Which would lead to the question, why didn’t GNE convert them to Euro 6 hybrid, rather than Euro 6 diesel. Was it to save on the cost of refurbishing/replacing possibly life-expired batteries?