My wife and I have flight from Saudi to Geneva round trip by BA. On my flight back I have a layover for about 10 hours in London. I would like to visit London and I do not have UK visa. I have a USA visa but wife does not have one. Is it possible for both of us to enter London?
You can check what kind of visa you need to transit in the UK here. However the short answer is that both of you need a visa to transit in the UK.
You can apply for either an Airside visa, in which case you cannot leave the airport, or a Landside visa which will allow you to pass through immigration and visit London