Britain today filed its first criminal charges against US-based Libor traders, as the UK arm of a complex global investigation into alleged benchmark interest-rate rigging stretches across the Atlantic.

The Serious Fraud Office (SFO) charged three former traders at British bank Barclays - director of dollar fixed-income swaps Jay Merchant and dollar interest rate derivative traders Alex Pabon and Ryan Reich - with conspiracy to defraud in connection with its Libor inquiry.

A provisional hearing has been scheduled for the three men, who the SFO confirmed were currently in the United States, at Westminster Magistrates Court in London on May 27th. Their lawyers were not immediately available to comment. The charges could prompt the first extradition to Britain from the US in the lengthy investigation into the alleged rigging of Libor (London interbank offered rate), a central cog in the global financial system.

The SFO declined to comment on any extradition request or give further details about the charges. The investigation into benchmark interest rates has been overshadowed by a parallel inquiry into allegations of foreign-exchange market rigging, which on March 5th reached into the heart of London’s financial establishment when the Bank of England suspended a staff member.

However, the inquiry into alleged fixing of Libor and related Euribor rates, against which around $450 trillion of financial contracts from derivatives to consumer loans are priced, has so far seen US and European authorities fine 10 banks and brokerages $6 billion and charge 16 men.

The SFO in February charged three former London-based Barclays Libor submitters - Peter Johnson, Jonathan Mathew and Stylianos Contogoulas - over a two-year scheme to rig rates and in March charged three former ICAP brokers with fraud-related Libor offences.

Reuters