I saw slower in the Gower (South Wales) in the Summer. Wor Lass and I watched this guy clean the Tourist Centre at Rhossili, and honestly, you won't get slower than him.
I swear, this place - even on ladders - shouldn't have taken long:
I found a pic of it on Google:

The window cleaner:
1. Brushed the frame and window with a hand brush.
2. Really scrubbed the windows with a small washer; but really scrubbed them.
3. Scrimmed the side and top edge.
4. Did pull down strokes with a small squeegie, drying the blade after each pull.
5. Scrimmed the frame again.
All done with meticulous effort.
I swear on my dog's life (bless him), that we went down to Rhossili beach, messed around, ate some food, walked back, and he was still there working away.
I wanted to go and help the guy out, but declined since I didn't want to be a 'You don't wanna do it like that...' 'Arry Enfield type; but he's the slowest.
Anyone know him?