Mark was very flexible and helpful. He met us in front of the building and showed us the apartment. Besides he gave us wonderful advices about the sight seeings and restaurants in Prague, which turned out to be really useful.
The apartment itself was in good condition and was very spacious for three adults. Location VERY central. Unfortunately it was extremely hot (about 38 degrees in the day) while our stay in Prague. Despite two fans we had to sleep on the floor. And it's noisy late in the night and early in the morning, for we had to keep the windows open because of the heat.