Actually, I think the pic is a bit deceiving really. I don't think I could even reach that with my 25ft SLX.
I do G/1/2 with a 5 x 5ft SLX on flats with standard ceiling height. I have to reach a little on one side where the ground falls away. That's why I suggested 30ft to make sure because it looks like that building has slightly more than standard ceiling height. Looks like it might be 12 - 18" higher per floor so perhaps a 5 x 5 won't quite do it.
MODIFIED TO SAY: Sad git that I am, I just saved the pic and enlarged it. Although blurred, I attempted to count the courses of bricks. From ground to top of highest window looks like 33ft 3". Looks like I should eat humble pie. Probably could do with a 35 footer. Pics can be so deceptive sometimes. Although it's possible to allow for reach and call it 30ft, that is only the vertical distance. By the time you've stepped back it can easily add a few feet. I reckon 35ft pole length (not reach) to make sure.