Take a sight seeing bus tour in London?

Have never taken the hop on/off tour so don't know the route. I do live in a city where traffic rules though, the megalopolis of LA, and always give myself at a minimum an hour to get virtually anywhere except the corner market which I walk to. Depending on where you are catching the bus and the route to the Palace I'd calculate the same amount of time. Traffic in London compares to LA's on bad days. As a fall back and in order to assure yourself a good vantage point for the pomp and circumstance you could get up early and ride the tube. If it's a week day you'll find commuters but hey it's part of the experience. Weekends mostly tourists. If you rode to the Westminster station you could exit at Parliament square and stroll up Birdcage Walk past St. James park to the Palace. Lovely walk. You could also tube to Green Park, exit and walk through Green Park over to the Palace or finally, exit at the Hyde Park Corner station, walk out and over to the Wellington Arch and down the road alongside the Palace to the Victoria Memorial. As you can see I'm big on walking and experiencing the sights and sounds of London. Hopefully others who have used the Hop On/Off bus will chime in and answer your question.

I was just in London for a few days in May of 2014. I paid for the "Big Bus" tour for 2 days, thinking it would be a quick way to get around and learn a lot. I wouldn't do it again. I get the impression that the bus is a great idea for getting an overview of the city, and maybe getting off once you've done the whole 2 hour tour and know exactly where you want to land. I found that it took a long time to get from place to place, and the Big Bus only traveled one way at most stops. That proved to be a big pain. If you do the tour, I would only do one day for sure, and be certain you get a live guide rather than an audio guide. Have a wonderful time!

I can only say what our experience was. We paid the relatively expensive price for the hop on/hop off bus and we got about an hour in to the tour, which was a nice way to get to see a lot of areas in central London quickly. But, traffic is horrible there and our bus got stuck in a traffic jam and didn't move for about 30 minutes (the poor tour guide was running out things to tell us because the scenery wasn't changing). We got off and didn't go back on. That was after they told us that they could not take us by Buckingham Palace that day as the route they normally cover in the part of town was too bogged down with traffic. Long-winded answer to your specific question - beware of relying on any above-ground transportation in London to make short deadlines.

All this advice is pointing away from using the bus tour, especially during morning rush hour. Tube is also crowded in the morning, but runs much more frequently.

We have used Evans-Evans Tours, numerous times. The day tour of London, includes the Changing Of The Guard. We enjoyed all of the tours, booked through them, for many trips there.