This is the rucksack used by one of the Thurday's London bombers on the number 26 bus. The image isn't great but if you look closely you would be able to see that it is a Fitness First bag.
This bag is very common on the Tube and used by possibly thousands of commuters everyday. I am not a member of Fitness First so I do not know whether there is a policy that requires its members to use such bags when going to one of its gym (it would be a stupid policy). Anybody care to enlighten me?
According to yesterday's Evening Standard, the picture was taken by a resident on a third floor flat.
(Update: uploaded the picture from Evening Standard, it's clearer)
Via Tube Diary:
I have a decent enough Maglight that I received for my birthday many years ago (I hardly use them unless I have to walk through the woods at night). My whistle still works from when I bought it during one of the Notting Hill Carnival I attended (like hell I will bring this with me, what am I in? Titanic?). I always carry a bottle of water. And this bunch wants to sell all of these plus a mask for twenty quid.
Paranoid. But nothing wrong if you are. Just get them from your local store. Cheaper too.