They have put together a focal length comparison, showing what Buckingham Palace looks like at 1200mm and beyond. You can find out more about the lens' outing to London in the video above.
MPB acquired this super rare Canon lens recently, and it is currently on sale on their website for a whopping £99,000! It's very rare that a lens like this becomes available, and it's thought that this is currently the only one available in the UK.
You can find out more about the lens, and the results of the focal length comparison on the MPB Updates page.