Both have held (or still hold) executive roles at Facebook. Both are based in London. Both have children. Both are very powerful. Meet Baroness Joanna Shields and Lady Nicola Mendelsohn; two of the most high-profile women working in the UK technology sector. 

In the Tory-blue corner, weighing in at "Baroness", we have US-born Joanna Shields.

The title for the most powerful woman working in the UK tech sector is hotly-contested ©iStock/kontrec
The title for the most powerful woman working in the UK tech sector is hotly-contested ©iStock/kontrec

The 52-year-old businesswoman was born in Pennsylvania as the second of five children. After studying a science-related degree at Penn State University, she went on to gain an MBA from George Washington University and it wasn't long before she made her first strides into the technology sector.

Starting out at a number of small Silicon Valley firms, Shields quickly climbed the ladder and before long she became CEO of an interactive video technology company called Veon, which was acquired by Philips in 2000. 

Over the last two decades, Shields has played a fundamental role in the growth of some of the world's biggest technology companies, including Google, Bebo, AOL and Facebook. Two of her most senior roles were at Google and Facebook, where she was Google MD of Europe, Russia, Middle East & Africa and Facebook VP and MD of Facebook EMEA.

However, not satisfied with working in the private sector, Shields decided to turn her attention to the UK government, possibly because she knew her experience in Silicon Valley could prove useful to many of the policy makers and technology companies in the UK. 

In 2012, she was given the role of spearheading the UK technology sector on behalf of prime minister David Cameron through the Tech City UK organisation. In addition to being CEO and chair of Tech City UK, she was also made the UK ambassador for digital industries. But Shields, a woman who appears to be driven by success and status, didn't stop there. 

She later became a special advisor to David Cameron on the digital economy and a non-executive director at the London Stock Exchange. 

Perhaps the biggest recognition of her work in the UK came in 2014 when she was awarded an OBE in the New Year Honours List for "services to digital industries and voluntary service to young people". She was elevated to the peerage on 16 September 2014 taking the title Baroness Shields, of Maida Vale in the City of Westminster. 

While Shields may sound impressive, other women in the UK have also climbed the slippery tech career ladder. 

Facebook's Nicola Mendelsohn

In the not-so-red Facebook corner, weighing in at "Lady", we have British-born northerner Nicola Mendelsohn – Facebook’s most senior employee outside of the US.  

In 2012, after over 20 years in the advertising industry, Mendelsohn joined Facebook to lead the company’s operations across Europe, the Middle East and Africa.

She has held director and board level roles for a number of large and prestigous organisations, including Women's Aid, the Creative Industries Council and the Grey Communications Group. 

Today, the Leeds University English and theatre studies graduate works under Mark Zuckerberg from Facebook’s new UK headquarters in a Euston skyscraper but it’s understood that the mother of four is constantly travelling around the expansive region she oversees, to the extent where she has to plan her diary a year ahead.

Someone who works for Facebook may not instantly strike you as the most powerful person but when you look a little closer there's probably a case to be made. 

With a valuation that exceeds the GDP of Malaysia, Facebook is now one of the richest companies in the world, and the EMEA region overseen by Mendelsohn plays a significant part in that success.

Further, Facebook has its fingers in a number of pies, from advancing drone technologies and delivering internet to the world's entire population through, to developing new artificial intelligence.

So, now you’ve had the spiel, let’s get back to the issue of who is the most “powerful”. It’s always a tough question given there are so many definitions of what constitutes power. But let’s have a go anyway.

Well, when it comes to shaping policy, it’s likely that Shields, whose office in Number 9 Downing Street, will have the upper hand in driving forward new legislation. This could involve everything from what the next generation are taught at school through to how much tax Silicon Valley companies pay on their UK profits. But Facebook’s vast budget and its deep interest in uncovering and supporting new technologies means that Mendelsohn also wields a great deal of power. While many of Facebook’s high-level decisions will be made by CEO Mark Zuckerberg and his army of executives in Palo Alto, Mendelsohn is ultimately responsible for driving the company in EMEA and with 27 million UK users coming online every day in the UK alone, she’s certainly got access to a lot of people to make friends with.