Probably a tube stationary Olympic torch.
mobile phone mast
It's huge, isn't it. I'd have to include a mobile phone mast in my options, but haven't seen one this size before. So, other options - could it have anything to do with the digital switchover? A signal booster? Or, police/emergency services comms?
Aha - an answer via our Facebook page:
There are four on the Harringay passage: one is between Beresford and Allison, I can't remember the others. Most stench pipes were installed at the same time as the main sewers were built in the mid 19th century and as such can be rather elaborate. Ours are quite dull but I spotted some nice ones near London Fields. I'm sure that somebody once told me that the Victorians experimented with using the methane as a form of gas lighting and thus there are stench pipes that double as gas lights ... I have never quite beleived this! You can also trace the path of the underground rivers via the stench pipes - these were all vented after the Fleet exploded in the 1840s.
So yes, I was right: a methane powered Olympic Flame. I'm sure all beer drinking rugby players could explain the principle er behind it.
I feel postively enlightened - had never heard of stench pipes before! There's a whole blog devoted to London's Victorian pipes, should you feel inclined... http://stinkpipes.blogspot.co.uk/
You might be also enlightened to know about SEWER GAS LAMPS! yes, sewer gas used to light the streets in some parts of the UK. I don't believe that the Turnpike Lane mast is a sewer gas pipe though, why would it have that wider section on the upper half? I think more likely it's a communications mast. Just my opinion :)
There is one on Pemberton Road, I remember looking up once and thinking it was a rather long pole! I now know what it is!! I feel like i've learned something I never thought i'd need to know
There used to be one on the corner of Avondale and Conway Roads until it fell (rather dramatically) into the front garden of a neighbour!