Last checked at 
(Repeats story published late on Tuesday)
* Thursday's election highly unpredictable and pivotal
* Bankers and traders cancel leave, set to work all night
* Big banks deploy extra staff in London, NY, elsewhere
* Sterling set to react first to early election results
* Eyes will then turn to HK-listed banks, Australia miners
By Elizabeth Howcroft, Lawrence White and Saikat Chatterjee
LONDON, Dec 10 (Reuters) - It's the time of year when
London's bankers and traders wind down and prepare for holidays.
Instead, many are cancelling leave and will work all night on
Thursday as Britain votes in an unpredictable election that
could convulse global markets.
Major banks including Barclays and HSBC
also plan to deploy extra staff through the night, not just in
London but also on trading floors in New York, Hong Kong and
Singapore, to make sure they're constantly on call for clients.
This may seem an oversized reaction in an age where trading
is increasingly reliant on robots, but this is a financially
pivotal event where investors could make or break fortunes. It
is Britain's first December election in almost a century, and
Brexit itself could be on the table.
Prime Minister Boris Johnson's ruling Conservative Party is
running on a pledge to enact a swift split from the EU, while
Jeremy Corbyn's main opposition Labour is promising another
referendum on membership of the bloc.
"I just basically cancelled all holidays for our trading
team next Friday, because we had some people actually who tried
to take leave, this has all been cancelled, which gives you an
idea about what I expect on that day," said Marco Pabst, chief
investment officer at big Swiss private bank UBP.
"I think Brexit day is going to be a walk in the park
compared to a Corbyn majority - and Brexit day was bad."
The pound plunged more than 10% in the immediate aftermath
of Britain's vote to leave the European Union in June 2016,
while $2 trillion was wiped off world markets.
While the prospect of a second Brexit referendum could be a
positive for sterling, countering factors could be Corbyn's
policies to nationalise parts of the economy, as well as further
uncertainty as Brexit is delayed once more.
London is the world's biggest centre for the global $6.6
trillion a day foreign exchange markets and the biggest hub for
secondary bond market trading, meaning any Brexit-fuelled
volatility can have global implications.
'ADRENALINE KEEPS YOU GOING'
Of the many outcomes possible, market watchers fear an
outright Labour Party win as the most damaging one for markets,
even though markets assign it a very low probability.
British mid-cap stocks with high exposure to the domestic
economy have rallied more than 8% since October while the pound
has gained nearly 7% versus the euro to a 2-1/2 year high at 84
pence as markets have increasingly factored in a Johnson win.
Opinion polls have consistently shown the Conservatives
holding a healthy lead, yet the pollsters failed to accurately
call the last two British elections and dramatically dropped the
ball on Brexit and Trump.
Exit polls on Thursday will begin at around 2200 GMT, after
voting closes, with a Nomura analysis indicating that if they
produce a surprise, sterling will react.
Then the official results will begin to trickle in.
Of particular interest will be results from Sunderland and
Newcastle-upon-Tyne, which will arrive from 2330 GMT. While all
the six seats there are expected to stay Labour, any signs of
Conservatives over or under-performing will be seized upon as
signposts to a national result.
Jonathan Pryor, head of foreign exchange sales at Investec
in London expects these early results will be when clients would
first want some insights on the broader picture.
"Obviously it's not easy to stay up all night and the small
hours are the hardest bit, but the adrenaline keeps you going."
FIRST TO MOVE: STERLING
There will be no let-up in 24-hour global markets.
Sterling will be the first to react to the early results,
according to market players, with the pound versus the dollar
and euro the key crosses to watch.
The next potential movers will be the shares of major banks
listed in Hong Kong, namely Standard Chartered and
HSBC. Next up could be the United Kingdom exchange
traded fund, an instrument that allows investors to trade
UK-focused stocks outside British hours.
Then financial eyes turn to miners listed in Australia.
The election is taking place at a time when investors have
typically shut their trading books for the year which means any
market volatility could be exacerbated. Risk managers are
testing electronic trading systems to ensure there are no
glitches in case market volatility jumps sharply.
Expected price swings for the pound over a one-week period
as measured by derivative gauges is running at around 11%, more
than double July's reading, and traders expect it to jump
further as election results start coming in.
Some investors such as Kaspar Hense, a portfolio manager at
BlueBay Asset Management in London who helps manage $60 billion
in assets, said it might simply be best to steer clear.
"We have closed our long sterling position going into
election night," said Hense. "There is too much risk."
(Reporting by Elizabeth Howcroft, Tommy Wilkes, Sinead Cruise,
Lawrence White, Thyagaraju Adinarayan, Alistair Smout and Saikat
Chatterjee; Editing by Pravin Char)
