Sisse Bohart, a 41 year-old Dane, told a jury at Southwark Crown Court that the trial was focusing on a routine and small part of a job she did 12 years ago that took just minutes of her day.

Supported by her mother, two step sisters and two brothers in the public gallery, Bohart said she had been told by superiors to accommodate trader requests for rates if she could.

But she said she had been unaware that traders were discussing how to influence benchmark rates with peers at other banks until she saw the case against her.

Asked by her lawyer Amanda Pinto how she would have reacted to inter-bank contacts had she been aware of them at the time, she said: "I would have spoken to Colin (Bermingham, her boss) because my first thought when seeing it is it is wrong."

Bohart, Bermingham, Italian-born Carlo Palombo, German Achim Kraemer and Philippe Moryoussef, who is being tried in absentia, each deny one charge of conspiracy to defraud by dishonestly manipulating Brussels-based Euribor between 2005 and 2009.

The group, aged between 39 and 61, is the first to be charged in relation to Euribor, the euro counterpart of the London interbank offered rate (Libor) - crucial benchmarks for around $450 trillion (339 trillion pounds) of financial contracts and loans worldwide.

Euribor and Libor are average interest rates calculated after submitters at a panel of major banks report their banks' estimated costs of borrowing from each other over differing borrowing periods to an administrator.

The Serious Fraud Office (SFO) prosecutor argues that bankers deliberately disregarded that these rates should be set independently of commercial interests, prejudicing the economic interest of others.

Bohart, who joined Barclays as an IT desktop support worker in 2002 before becoming a junior trader and rate submitter in 2004, said she had always acted openly. She sat between two senior managers, all conversations could be heard and communications were monitored, she said.

"I followed what I believed was the right way of doing things - how I saw things being done and told by my manager Colin Bermingham," said Bohart, who has an 11-month-old son.

She described Bermingham as a very caring, supportive, knowledgeable and honest man, who often drove her to the airport on a Friday so she could fly home for the weekend to be with her sick step-father and, later, to see her boyfriend.

At times emotional, Bohart said she had been shocked when SFO officers called her in November 2015 on her mobile phone while she was at work in Sweden, seven years after she had left Barclays in 2008.

Asked why she had come voluntarily to be tried, she said:

"I believe that when you have done nothing wrong it should be OK to stand and tell my story."

(Reporting by Kirstin Ridley; Editing by Mark Potter)

By Kirstin Ridley