Amrit Santhirasenan once wrote an HR policy on the back of the 185 bus. He has also taken a call from a potential investor while bathing his daughter. For anyone tempted to picture entrepreneurship as an uninterrupted sequence of whiteboards and decisive handshakes, these are useful corrections. Sometimes the next stage of a company’s development has to fit between a bus stop and the end of bath time.
The company was hyperexponential, usually shortened to hx, which he co-founded with Michael Johnson in 2017. It began as a two-person operation in his kitchen. Its subject was insurance pricing: a field in which a questionable assumption can become an expensive promise. The founders had worked with the problem themselves. They were qualified actuaries who could write software, with a fairly precise idea of what their tools ought to do.
That combination runs through Santhirasenan’s career. He understands the appeal of an elegant technical solution, and the disappointment when it fails to help the person doing the job. His route into entrepreneurship took him through computer science, insurance, London and Toronto. The recurring activity was building something that had previously been missing.
The software graduate takes a detour
At the University of York, he studied computer science. His 2005 undergraduate dissertation appears in a supervisor’s teaching record under the title Animating Term Rewriting Systems. It is an appealingly technical opening credit for someone whose later work would require him to explain complicated systems to rather different audiences. The computing came before the insurance vocabulary.
He has described entering the industry after deciding that the aftermath of the dot-com bust made software engineering look an unpromising career choice. People suggested actuarial work to someone who liked mathematics as well as technology. He discovered that he enjoyed it. A detour acquired the permanence that detours sometimes do when the work turns out to be interesting.
His insurance career began at Catlin in 2005. By 25, he was being sent to Toronto to establish the actuarial function for the company’s Canadian operations. This meant creating a function from the ground up, an early encounter with the difference between doing a technical job and arranging for a group of people to do it together.
There is a practical continuity between that assignment and the business that followed. A team needs a way to turn specialist knowledge into work other people can use. Later, at Tokio Marine Kiln, he became the company’s first pricing actuary and built a pricing and analytics function bringing together actuaries, data scientists and developers. His interests had found a common office.
The tool he kept looking for
At Tokio Marine Kiln, the frustration became specific. He wanted sophisticated pricing software suited to the sparse and unusual information encountered in specialty insurance. He wanted actuaries to retain control of their models. Excel had limits, and the available alternatives did not meet the need he saw. Looking for the right product eventually became the prelude to starting a company.
The nature of the data matters. Specialty insurers cannot always rely on vast collections of conveniently comparable cases. The information can be small, fragmented and awkward to work with. A clever model alone does not resolve the practical work of getting that information into a form that supports a decision. The person writing the model and the person using its result need a workable connection.
Santhirasenan had spent 12 years in the Lloyd’s and London markets before founding hx. That gave the venture a particular starting point: familiarity with the work, its habits and its frustrations. Michael Johnson brought the same combination of actuarial and software experience. Their product, Renew, was built for people developing and using insurance pricing models.
In 2019, the company joined Lloyd’s Lab Cohort 3. The programme gave it a structured way to work with prospective customers and others in the market. Its objectives included testing the platform, working on pricing practice and collaborating with fellow participants. For a product meant to connect specialists, learning in company was a sensible form of development.
“Come for the fun opportunities, stay for the insurance.”
Amrit Santhirasenan, on recruiting people to hx
He speaks about insurance with an enthusiasm that can surprise people arriving from technology. Richard Gunn, now a senior hx leader, has recalled a meeting in which Santhirasenan and Johnson discussed the overlap between the two fields with rocket-launch intensity. The enthusiasm had a recruiting effect. An industry’s reputation and the experience of working inside it can be quite different things.
A kitchen, a bus, a family timetable
Knowing the product problem did not supply a ready-made education in running a company. There were policies to write, investors to speak to and interruptions that resisted the tidiness of a plan. His accounts of the kitchen-table beginning and the 185 bus preserve the useful awkwardness of that period. The business needed an HR policy whether or not its founder had reached a desk.
Parenthood supplied another set of obligations. The investor call during his daughter’s bath time is memorable because both sides of the situation are so ordinary. The call matters; so does the bath. A startup’s demands do not arrive in a separate, conveniently bounded compartment of life. His early business story contains a child because his actual life did.
He turned that overlap into Startup Dads, a podcast about building businesses and raising children. Its premise was to bring business leaders into a conversation about both responsibilities, and the lessons that might travel between them. The host was participating in the question he was asking. Running a growing company and being a parent were already sharing his timetable.
The podcast adds something useful to his public biography. Pricing software explains what he chose to build. These conversations show another subject he chose to spend time on: how people manage responsibility when several things matter at once. The willingness to discuss that problem gives the polished company milestones a more recognisable human scale.
Checking the people with the cheque
Highland Europe’s investment story contains a pleasing reversal of the usual scene. While the investor assessed hx, Santhirasenan checked the investor with its portfolio-company founders. The due diligence ran both ways. He wanted to understand the people who would become part of the company’s working life, including what happened after a deal was signed.
Highland announced an $18 million round in June 2021. In January 2024 came a $73 million Series B led by Battery Ventures, with participation from Andreessen Horowitz and Highland. Guidewire co-founder Marcus Ryu and a16z partner Angela Strange joined the board. The funding brought experienced enterprise-software investors into a company shaped by insurance practitioners.
The financial context made that round interesting. European technology investment had fallen sharply in 2023. Santhirasenan argued that investors still wanted growing businesses capable of sustaining themselves. At the time of the announcement, hx reported that sales had increased tenfold since its Series A while it remained profitable. He framed the capital as a way to bring in expertise and support expansion.
Led by Battery Ventures, with a16z and Highland Europe participating.
The amount is a milestone, but it also raises a more personal question: what does a founder want from the next set of colleagues? Santhirasenan’s reference checks offer one answer. He approached a relationship with consequences as something worth investigating. An actuary doing his homework is perhaps less surprising than an investor being assigned homework’s equivalent.
The decision still belongs to someone
By July 2026, the company’s ambition had widened from pricing models to more of the underwriting workflow. At hx Live London, Santhirasenan demonstrated hyperoperator, an AI agent coordinating work across the platform. The launch announcement described a broker submission becoming a triaged and priced cyber risk in under three minutes, without manual data entry. Controlled customer rollout was planned for later that year.
The important qualification is in the surrounding rules. The proposed workflow operates within an insurer’s pricing logic, appetite and authority controls. It can prepare work for review and escalate where judgment is required. Santhirasenan’s own formulation was compact: “hyperoperator gives underwriters leverage without taking judgment out of their hands.” The person responsible for the decision remains central to the pitch.
A September 2026 survey commissioned by hx offered a reason to keep that distinction in view. Among 350 senior commercial insurance professionals in the UK and US, 44% named the loss of senior judgment without its being passed on as their leading fear. Only 15% said their firms had found a way to capture what their best underwriters knew.
Two separate survey questions. Base: 350 UK and US commercial insurance professionals. Commissioned by hx; fieldwork by Coleman Parkes.
Those findings are a useful companion to a fast demonstration. A file can move quickly through a system while the understanding behind a decision remains difficult to preserve. The survey describes a concern that software has to take seriously: experienced people know things their organisations struggle to record. Speed makes an attractive stage performance. Knowledge transfer is slower to applaud.
Santhirasenan’s career keeps returning to the space between expertise and its use. In Toronto it involved building a function. At Tokio Marine Kiln it involved assembling different disciplines. At hx it became a product and then a company. The work now carries the vocabulary of AI, but the question is familiar: how do you help someone make a better decision with what they know?
It is a substantial question for someone who has also had to decide when to answer an investor and where to write an HR policy. The grand ambitions and the small practical arrangements belong to the same biography. Somewhere between the model and the meeting, the company still needs people to make the day work.