Senior Executive Assistant (to CEO) in London

About us PhysicsX is a deep-tech company with roots in numerical physics and Formula One, dedicated to accelerating hardware innovation at the speed of software. We are building an AI-driven simulation software stack for engineering and manufacturing across advanced industries. By enabling high-fidelity, multi-physics simulation through AI inference across the entire engineering lifecycle, PhysicsX unlocks new levels of optimization and automation in design, manufacturing, and operations — empowering engineers to push the boundaries of possibility. Our customers include leading innovators in Aerospace & Defense, Materials, Energy, Semiconductors, and Automotive.

As we continue to grow, we're looking for an exceptional Senior Executive Assistant to be a right hand to our CEO. This is a high-intensity role — priorities shift daily, the CEO moves fast, and you'll need to be comfortable holding things together in the background when not everything is certain. It's also an exciting place to be: at the heart of a fast-growing deep-tech company, working closely with leadership on some of the most consequential deals and decisions the business is making.

The Role

As Executive Assistant to the CEO, you will be a trusted partner and thought partner — ensuring the CEO's time and energy are aligned with the company's highest priorities, anticipating and solving problems before they arise, and keeping execution moving across a wide range of internal and external engagements. As the company evolves, you should expect to also provide support to 1–2 other leaders, and be flexible as that remit grows. This is a role for someone deeply detail-oriented, who exercises strong initiative and adapts quickly to shifting demands. The CEO's schedule is genuinely fluid — where he'll be next week is often not fixed — and you'll need to be comfortable managing scheduling and logistics in that context, making sensible decisions without complete information and adjusting when things change. You won't always be told what to do next, and not everything will go to plan. You'll need to adapt quickly, reset, and keep moving.

What You'll Do

• Own the CEO's calendar end-to-end: manage rapidly shifting priorities, hold the line on competing demands, and make active trade-off calls between customer meetings, internal commitments, board/investor asks, and team time — bringing the CEO in only when a real judgment call is needed.
• Own and manage the CEO's inbox — triaging, prioritising, and ensuring clarity and timely responses on the most important matters.
• Stay fully embedded in the flow of the CEO's priorities — staying on top of what his teams are working on, sitting in on key meetings for context, and following up on actions.
• Coordinate complex scheduling, travel, and meeting logistics, often across multiple time zones and with senior external stakeholders — own complex domestic and international travel including multi-city trips, last-minute re-routing, and events, and build the muscle to rebook and reshape an itinerary inside an hour when plans change.
• Liaise confidently with internal teams, customers, board members, and investors on behalf of the CEO.
• Build and maintain working relationships with the assistants of senior customer and partner contacts — coordinating scheduling across multiple offices and being a reliable counterpart they trust.
• Lead planning and delivery of board meetings and other key events.
• Prepare and manage documentation including NDAs, briefing materials, and follow-ups from meetings — pulling together briefing packs, agendas, attendee bios, and pre-reads in advance of customer, partner, and executive engagements including CEO and Board-level conversations.
• Monitor and communicate across multiple channels (email, Slack, WhatsApp, verbal) with clarity and professionalism.
• Provide cover for other EAs across the UK, US, and Singapore when needed.

What You'll Bring

• Minimum 3 years' experience supporting senior leadership, ideally at C-level, in a dynamic, fast-paced environment.
• A proactive, strategic mindset — able to anticipate and plan ahead for the CEO's evolving priorities.
• Confident self-starter who takes initiative and isn't afraid to proactively chase the CEO or other senior stakeholders for the decisions, information, and sign-offs needed to keep things moving.
• Resilient and even-keeled — genuinely comfortable with ambiguity, including the practical reality that the CEO's location or schedule for next week may simply not be confirmed yet.
• Outstanding organisational skills and attention to detail, with strong written and verbal communication.
• Strong judgment under ambiguity — comfortable making decisions on the CEO's behalf when he isn't reachable, and knowing the difference between a decision to escalate and one to make.
• Impeccable discretion — you'll see commercially sensitive customer information, partnership terms, financial and personal details, and confidential internal discussions.
• A natural network-builder — comfortable picking up the phone with an EA they've never met, and building the kind of rapport that makes complicated multi-stakeholder scheduling happen.
• Enjoys working with diverse personalities, building relationships, and contributing to a social, inclusive team environment.
• Experience working across time zones and within international organisations is a plus.
• Already uses AI tools — Claude, ChatGPT, or similar — as part of their daily workflow: drafting communications, summarising long threads, prepping briefings, organising notes.
• Familiarity with Notion and Slack is a plus.
• Proficient in Microsoft Office (Outlook, Word, Excel, PowerPoint) — required.
• Genuinely flexible — what was the plan this morning may not be the plan this afternoon, and that needs to be fine.
• Support outside standard hours is part of the role; we offer the same flexibility in return.

What we offer

• Build what actually matters: Help shape an AI-native engineering company at a formative stage, tackling problems that genuinely matter for industry and society.
• Learn alongside exceptional people: Work with a high-caliber, collaborative team of engineers, scientists, and operators who care deeply about doing great work, and about helping each other get better.
• Influence over hierarchy: We operate with a flat structure: good ideas win - wherever they come from.
• Sustainable pace, long-term ambition: Building meaningful technology is a marathon, not a sprint.
• Equity options - share meaningfully in the company you’re helping to build.
• 10% employer pension contribution - because investing in future matters.
• Free office lunches - to keep you energised and focused.
• Enhanced parental leave - 3 months full pay paternity and 6 months full pay maternity leave.
• YellowNest nursery scheme - to help working parents manage childcare costs.
• 25 days of Annual Leave (+ Public Holidays) - because taking time to rest matters.
• Private medical insurance - 100% employee cover.
• Wellhub Subscription - gain access to thousands of gyms, classes and wellness apps.
• Eye tests - because good work depends on good health.
• Personal development - dedicated support for learning, development, and leveling up over time.
• Employee Assistance Programme (EAP) - confidential wellbeing support, available whenever you need it.
• Bike2Work scheme and Season ticket loan - to make getting to work easier and greener.
• Octopus EV salary sacrifice - for a simpler, more sustainable way to drive electric.

We value diversity and are committed to equal employment opportunity regardless of sex, race, religion, ethnicity, nationality, disability, age, sexual orientation or gender identity. We strongly encourage individuals from groups traditionally underrepresented in tech to apply.