Ah, if you were looking for a backpack that does it all. Kipling might have just the thing for you. Just take a look at the Seoul backpack, a lightweight style that's got multiple compartments, including a padded one perfect for your laptop. But that's not it, it's also water resistant, so London-weather (or any other rainy city, for that matter) will have nothing on you.
Kipling backpack
Zip closure
Top handle, adjustable backpack straps, water resistant, padded pocket for laptop, pouch pocket for wallet, mobile phone pocket
Height 44cm, depth 20.5cm, width 35cm
Capacity 27L
100% polyamide