CircleRock’s bold US play: A Fortune 500 heavyweight joins the team

CircleRock Capital, the venture capital syndicate firm, has appointed Paul Calatayud as a partner, as the Irish business continues to expand its presence in the United States.

Calatayud is a five-time chief security officer (CSO) with experience at major Fortune 500 companies, including Palo Alto Networks, which has a market capitalisation of $138 billion (€119 billion), and UnitedHealth Group, valued at more than $280 billion.

Calatayud joins CircleRock Capital’s cofounders Barry O’Neill and Conor Sharpe as the firm sets up its first permanent investment vehicle alongside its existing deal-by-deal business. CircleRock has previously appointed venture partners like Sarah Irwin, the former head of legal with Tines, and Mark Maxwell, a scout with Sequoia Capital.

However, Calatayud’s role is different. 

“Paul’s joining as a Partner, which is a step beyond our venture partner model,” Sharpe explained. “Our venture partners work with us on specific deals and bring incredible domain expertise, but Paul’s role is more integral and permanent — he’s an equal partner across CircleRock’s investment activities, both our upcoming permanent vehicle and the deal-by-deal investments he works on.” 

Calatayud has advised over 20 cybersecurity start-ups, helping 14 achieve successful exits. In 2022, he co-founded cyber insurance company Onda with Joe Lonsdale, an American entrepreneur best known for co-founding Palantir Technologies with Peter Thiel. 

“We’re thrilled to welcome Paul to the team. His network reads like a who’s who of enterprise technology — C-suite executives at Fortune 500 companies and founders of leading venture-backed firms,” O’Neill said. 

“Having direct access to decision-makers, particularly in the US, who can genuinely accelerate growth during critical scale-up phases is a game-changer.” 

Sharpe added: “We’re already seeing the impact as Paul works closely with our current portfolio companies to facilitate key introductions and strategic partnerships. This hands-on value creation is also a powerful differentiator when we’re competing for allocation in oversubscribed rounds.” 

“Founders want investors who can actively open doors, not just write cheques. Paul will be instrumental in leveraging his network to strengthen our advisory board and expand our US presence.”

According to Calatayud: “Conor and Barry have built an impressive firm that combines flexibility and speed with rigorous selection, allowing them to compete successfully in highly competitive rounds alongside major institutional players.”

“The quality of their portfolio to date speaks for itself, and that’s the kind of quality I want to support. I’m excited to leverage my US and global experience and relationships across enterprise and the venture ecosystem to help CircleRock’s portfolio companies navigate their most important inflection points. The right introduction at the right time can be transformative.”

Expanding into the US

CircleRock recently made its first two investments in the United States, expanding beyond its earlier focus on Irish, British, and European start-ups. Its first US investment was in NetFoundry, a technology security company that recently closed a $12 million Series A round led by SYN Ventures, the specialist cybersecurity fund founded by Jay Leek, former chief information security officer at the Blackstone Group. “Cybersecurity is a top strategic priority for the world’s largest enterprises,” Sharpe said.

“Networking is one of the most difficult aspects of cybersecurity, so we’re thrilled to support a pioneer like NetFoundry who has managed to end the tug of war between security and business velocity.” CircleRock has also participated in a $5 million seed round investment in Fleak, alongside 500 Global, Cisco Investments and Databricks. “Fleak is building the critical infrastructure layer between enterprise systems and AI, solving the first-mile data intelligence problem by making machine data universally consistent, understandable, and AI-ready the moment it’s created,” Sharpe said. 

From left: CircleRock Capital’s Conor Sharpe, Barry O’Neill and Sarah Irwin. Photo: Bryan Meade

“Paul played a key role in both US deals. He helped source the opportunities and led much of the due diligence. The founders valued his input so much that both NetFoundry and Fleak AI asked him to chair their advisory boards,” he added.

“Beyond that, Paul brought in strategic investors for both rounds — including some of the biggest companies in the world — which strengthened the cap tables and opened up important partnership opportunities. He’s also a shareholder in both companies, which speaks to his conviction in what they’re building.”

CircleRock invests across multiple sectors, but the arrival of Calatayud is expected to deepen its activity in cybersecurity.

“Whilst we’re sector-agnostic at our core, Paul’s CSO background certainly strengthens our capabilities in cybersecurity, and we’re already seeing incredible deal flow there because of his network and stature in the industry,” O’Neill said. “Will we do more security deals? Probably, yes — but not because we’re changing strategy. It’s because cyber isn’t really one sector anymore. Security touches everything now — AI safety, cloud infrastructure, identity, critical infrastructure, defence applications — it’s embedded in every category we look at.

“So whilst Paul brings deep security expertise, that doesn’t narrow our focus. It broadens our ability to evaluate opportunities where security is critical. We’ll still invest where we see the best opportunities; Paul just gives us sharper conviction when security is part of the equation.”

Setting up a permanent fund

Since CircleRock was founded in 2022, it has invested €50 million in 25 companies. It has co-invested alongside major international funds like Accel, Northzone, and Hedosophia.

“More than half of our portfolio has already raised hundreds of millions in subsequent rounds, demonstrating our track record of backing exceptional founders at the earliest stages,” Sharpe said. It was the only Irish venture capital firm to back Irish-founded hospitality tech company Nory at both seed and series A.

It also invested in AI code optimisation startup TurinTech AI. Greg Lavender, a former CTO of Intel, recently joined the business as a strategic advisor.

It also invested in SimpleStudy, the Duolingo for exam preparation, founded by Oisin Devoy and Phillip McKenna.

Sharpe said that CircleRock had built its business on a deal-by-deal basis but it was now looking at launching a permanent vehicle.

“Following interest hinted at the last time we spoke, we are pleased to announce we’ll be launching a more permanent vehicle structure alongside our existing deal-by-deal platform,” Sharpe said. “Several family offices requested this after missing opportunities due to timing constraints on our deal-by-deal investments.” 

“The new vehicle will maintain the DNA of our deal-by-deal approach while offering committed capital across our pipeline in sectors including AI, Cybersecurity, FinTech, and DeepTech,” O’Neill added. “For us, committed capital means clearer investment capacity and stronger negotiating position in competitive rounds, where we’ve already proven we can win allocation alongside major institutional players. For investors, it offers streamlined access to deals where we’ve proven our ability to secure competitive allocations in high-quality companies.”

“Prior to formally launching the fundraise, we have already secured multi-million pound commitments from leading family offices,” Sharpe added. “And we’ll maintain a strong emphasis on partnering with strategic investors who contribute to our reputation for genuinely adding value to early-stage companies beyond capital.”