We had a good time at Mark's apartment. The location is great! close to a couple of tube stations and Hyde Park is about a 10-12 minute walk away. Restaurants and pubs are walking distance. There is also a really nice Italian restaurant downstairs.
There are very clear check-in and check-out instructions, which is great! so overall, we had a good time. The flat is a little small, which I suppose is expected for central London. But I think it could have been a bit cleaner and more welcoming. The couch needs a deep clean or needs to be replaced. Apart from that, it was fine!