Court ruling in UK set to spark fresh sterling volatility
Investors have largely priced in the British government losing its Supreme Court appeal on whether it can trigger Brexit talks without parliamentary approval, but traders - both human and computer models - will scour the ruling for clues on whether the UK's devolved assemblies will get a say.
British Prime Minister Theresa May will learn at 09.30 today whether the court has upheld a High Court decision in November that her government must get approval from fellow Members of Parliament (MPs) before triggering of Article 50 of the Lisbon Treaty - the formal means of exiting the bloc.
The government is widely expected to lose its appeal - online spreadbetter Betfair is showing a 90pc probability that the Supreme Court will uphold the previous ruling.
But analysts said the ruling could contain many as-yet-unknowns, meaning sterling volatility - which has been elevated in recent months and drove the biggest one-day rise in the currency since the 1990s last week - is likely to spike around the time of the court ruling.
Key words that algorithm-driven trading models, which take up an increasingly large slice of currency markets, have been programmed to react to in a binary manner are likely to act as the initial sterling triggers, with human traders, who need more reaction time, following behind.
"It's not just a case of which way they rule - the exact wording of what sort of involvement parliament will have will be important," said MUFG currency strategist Lee Hardman.
"The knee-jerk reaction will probably be to see the pound strengthen, but the upside would probably be fairly modest on the back of that," he added.
Crucial among the unknown risks in the ruling - and therefore likely trigger points, analysts said - would be whether the Supreme Court rules that politicians not just in Westminster but also in devolved parliaments across Britain would have to approve Article 50 being triggered.
While the thrust of the case centres on whether the British parliament has to give its assent, the judges also heard arguments from the Scottish government and lawyers for Northern Irish challengers that Britain's devolved assemblies must give their approval too.
"A key risk would be if the court were to give Scotland's and Northern Ireland's assemblies a say, as that could trigger a potential constitutional crisis," Citi currency analyst Nishtha Asthan wrote in a note to clients.
If that ruling were to simply lead to a delay in the triggering of Article 50, however, without a crisis, investors said that could boost the pound.
Sterling was up as much as 0.8pc on Monday at a five-week high of $1.2472 ahead of the Supreme Court ruling. Against the euro, sterling rose 0.4pc to 86.16 pence.
"We are very bearish on sterling/dollar this quarter, but are wary that this week could see a correction into the $1.25-26 region," said ING's global head of EMEA research, Chris Turner. (Reuters)