I visited a motorcycle clothing shop and an aviation shop, but managed to keep my cash in my wallet. In a bookshop near Tempelhof I found a book all about eastern European motorcycles for 5 euros, and had a successful chat with the bookshop owners, who had been unaware there was a DDR Motorcycle Museum in their city. (They recommended the Spy Museum, which I visited on my first trip. Good guess.)
I returned to Arakin's flat using his spare keys, but was soon summoned out again to go to a very nice Chinese restaurant, where we dined in the company of another UK fur who has made Berlin his home. We followed this up with ice cream before heading back to the flat for a quick game of 10 Minutes to Kill.