there's a bit of a wind blowing up here. I haven't checked how things are in London; but I'm guessing the conference will be indoors, whereas the outdoors is always rather wild with dangerous humans and vehicles.

Senate building near the British Museum so more of a case of rushing outside to find freshish cooler air in between sessions in my experience.

London doesn't have any fresh air at all (unless you count outlying areas such as the huge gardens and ignore the pollen pollution). The old planetarium was my favourite / safest space for clean air.