The Serbia-born CEO of Nvidia-backed UK AI voice startup PolyAI has a nice way with words.
The US is the “new Rome” which “demands loyalty”, says Nikola Mrkšić; meeting his wife during a spell interning at Credit Suisse generated “very high ROI activity”; while PolyAI’s client base is “heterogeneous”.
Mrkšić is talking to Tech.eu in PolyAI’s commodious and new-looking basement offices (albeit sparsely occupied as it’s Friday and WFH Friday mania persists in the UK) in London.
PolyAI, which was founded in 2017 and valued at nearly $500m, is often cited in top ten lists of UK AI startups, a triumph which was given a boost last month when Nvidia’s man of the moment CEO Jensen Huang named it as one of its eight star startups (along with the likes of Wayve and Revolut), it would be investing in.
Serbian heritage
A namecheck by arguably the most famous businessman on the planet might have given the 30-something co-founder and CEO a moment to reflect on how his life had changed since his 1990s childhood growing up in troubled Serbia, in the aftermath of the breakup of Yugoslavia, its parent nation.
Mrkšić, who is slight in stature and softly spoken, says: “Serbia has had to find its own way after stumbling for quite a long time, which meant for my parents’ generation, it was a very like jaded feeling.
“And I think there was a reflex to push your kids into hardcore education so that they can rely on themselves and maybe be less dependent on the system, which had crumbled in front of their eyes.”
Growing up in Serbia, Mrkšić attended a Serbian maths high school (the equivalent of a UK grammar school) and was one of seven out of eight applicants who received a full scholarship to Cambridge University.
“We’re not designed to crack Cambridge interviews the way that many elite schools in Britain are”, he wryly points out.
His links with Serbia, where PolyAI has an office, are still strong, returning three or four times a year to visit friends.
Cambridge University
Serbia might be his home country, but London is where PolyAI was founded, seven years after Mrkšić came to the UK to study computer science and maths at Cambridge University.
He could have quite easily pursued a banking career, interning at Credit Suisse, where he met his wife during his undergraduate years.
But an encounter with Blaise Thomson, the founder of speech-related AI startup VocalIQ, a Cambridge University spinout, convinced him to join the startup as its first employee.
His time at VocalIQ, which went on to be acquired by Apple 18 months later, also lit the fuse for him wanting to launch his own startup, at a time when deep learning was gathering momentum.
During this time, Mrkšić also met his Taiwanese co-founders: Tsung-Hsien Wen (ex-Google), PolyAI’s CTO, and Pei-Hao Su (ex-Facebook), PolyAI’s SVP, engineering, at a Cambridge University group focused on spoken dialogue systems.
He says: “We were in high demand by the research labs. What frustrated us is that we didn’t really see automated voice improving.”
What PolyAI does?
PolyAI has developed AI voice assistants for call centres which guide customers through enquiries, handling millions of calls, which can, some say, sound indistinguishable from human voices.
PolyAI has worked with linguists to build voice assistants that reflect human speech patterns and the voices can be tailored by accent, tone and vocabulary.
The tech can complete many tasks a customer service rep can, including taking payment information as well as names, addresses and account numbers.
PolyAI uses its own proprietary large language models as well as frontier model companies like OpenAI and DeepSeek.
The early years of PolyAI, pre ChatGPT, were tough, says Mrkšić, given they were three researchers-cum-callow-entrepreneurs trying to commercialise a product that few in the business world knew about.
Back then, the scrappy startup, looking for commercial traction, speculatively approached London pub owners to experiment with its tech.
Competition and challenges
While PolyAI is making headway, automated call handling remains a turn-off for some people, partially due to historic bad experiences with rudimentary voice tech.
Furthermore, complex requests often require empathy and judgment that only humans can provide, experts say.
A McKinsey survey found that 71 per cent of Gen Z respondents (rising to 94 per cent for baby boomers) believe live, human calls are the quickest and easiest way to reach customer care and explain their issues.
Mrkšić has previously spoken about these challenges in the Tech.eu podcast.
Meanwhile, earlier this year Klarna CEO Sebastian Siemiatkowski said its AI voice approach led to “lower quality” and Klarna flipped from its AI-first policy to ensure customers always had a human to talk to.
Despite these challenges, it is easy to see why tech giants such as Google, Amazon and Microsoft have tried to crack automated call handling, as the call centre software market is estimated to be worth tens of billions of dollars.
Current startup competitors include the likes of Germany’s Parloa and US startup Rasa.
ChatGPT moment
The ChatGPT moment was a big boon for PolyAI, says Mrkšić, quadrupling inbound leads.
Now, PolyAI works with major businesses, amid growing enterprise 24/7 demand for call centre support, which suffers from high attrition rates.
These include Las Vegas casinos, Hilton and Marriott hotel chains, US delivery service FedEx, and the financial institution Unicredit.
Given the co-founders' stellar CVs, funding has not been a problem, says Mrkšić. Last year, PolyAI raised £50m in funding, valuing it at close to $500m.
The Series C was led by investors Hedesophia and NVentures, the VC arm of Nvidia, with participation from existing investors including Khosla Ventures and Point72 Ventures. It has previously raised $66m from investors.
It is understood that PolyAI will announce a fresh funding round later this year, likely to include fresh funds from Hedesophia and NVentures.
Relationship with co-founders
“I am the talker”, says Mrkšić, when asked how the founders divvied up the roles. He says he loves all the key functions of being CEO: fundraising, hiring and selling.
That said, he admits his management skills are a work in progress.
The three co-founders, he says, are still happily professionally married. “We are really close,” he says, but points out that there are clear demarcation lines.
For example, he says it was decided from day one that Mrkšić, a tech aficionado, would not write a line of code or voice any strong technical opinions.
He says: “I am deeply technical. I still very much enjoy the moments where I have time with product and tech teams to talk about things.”
In between running PolyAI, he also hosts an AI-infused podcast, discussing news and AI breakthroughs.
US footprint
Mrkšić has adopted a kind of second identity, as an American, as PolyAI’s revenues have grown in the US, which now accounts for roughly 80 per cent of its revenues, compared to 20 per cent in Europe.
He calls the US the “new Rome” which “demands loyalty”.
He says: “If you want to be successful in the US, you are going to use American spelling and work American hours.”
For example, when in London, he says he works from 10am to 1am UK time to fit in with the US.
He now spends a big chunk of his time in the US, where PolyAI has New York and San Francisco offices, meeting existing and new clients, meeting investors, and attending conferences.
The future
As AI becomes more commonplace and the frontier model becomes more effective, the tech, in theory, should improve.
PolyAI, which employs around 270 people, reported revenues of £11.9m in the year ending January 31 2025, up 75 per cent on the year, according to Companies House figures. Revenues were boosted by snapping up new customers and expanding existing contracts.
And what about PolyAI’s plans for the rest of the year?
Mrkšić says: “We have been growing the team like mad. So everything from accelerating on that and platform changes and announcements which are going to come towards the end of the year, opening up the ecosystem a bit more.”
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