Application Security Engineer in London

We insure small businesses and enable big dreams – not just for our customers, but for our people and communities too. With over 1,000,000 active insurance policies, we protect builders, bakers, landlords and more than 1,200 other trades. We’re a technology company as well as one that sells insurance. That means we build, we fail, we learn and we improve. Through our global social impact strategy, called 'The Big Dreams Project’, we're working to help 10,000 small businesses start or grow by 2030.

What Is the Opportunity? Here’s what you’ll be doing: We’re on a mission to build a tech-forward, secure environment that empowers developers rather than putting roadblocks in their way. As an Application Security Engineer, you’ll act as a core technical guide across our software development lifecycle—helping us embed security directly into our code and architecture while exploring next-generation defensive strategies like AI/LLM threat modeling. Unlike security roles where you’re isolated or acting as a gatekeeper, here you’ll be a genuine security champion. You’ll partner closely with engineering teams to demystify complex threats, modernise our DevSecOps practices, and mentor developers to build naturally resilient systems.

As one of our Application Security Engineers, you’ll:

• Provide expert guidance on secure coding, threat modelling, and OWASP Top 10 mitigation.
• Promote a security-first mindset across development teams, acting as a supportive technical mentor.
• Integrate security assessments, code reviews, and penetration testing seamlessly into the SDLC.
• Evaluate, implement, and run modern security tooling (SAST, DAST, IAST) to streamline vulnerability checks.
• Research emerging AI and LLM threat classes to design proactive, cutting-edge defensive architectures.
• Participate in incident response investigations and help deliver engaging security training.

We’re looking for someone who is:

• Experienced in application security (5+ years) with strong hands-on penetration testing and security tooling skills.
• Deeply knowledgeable about web vulnerabilities, secure coding practices, and cloud environments (AWS, Azure, or GCP).
• Familiar with DevSecOps methodologies and automated security integration.
• An open, clear communicator who can explain complex security concepts in plain English to both technical and non-technical teammates.
• Highly collaborative, empathetic, and passionate about mentoring engineers rather than just checking compliance boxes.
• Curious, proactive, and keen to stay ahead of modern threat landscapes like AI security.

We encourage people of all different backgrounds and identities to apply. We are committed to maintaining an inclusive, supportive place for you to be you and do your very best work. If you love dissecting complex systems, automating security right into the pipeline, and tackling emerging challenges like AI/LLM threats without the usual red tape, we’d love to hear from you.

What are the benefits of working at Simply Business:

• We offer a great work-life balance where workloads are manageable and everyone has the flexibility to work hybrid on top of the 25 days annual leave (plus bank holidays).
• We offer the option to buy five more days of holiday with your flexible benefits.
• Our flexible parental leave allows you to approach an important time how you want - with six months full pay to the primary caregiver and four weeks full pay if you're the secondary caregiver.
• Our life event leave is an extra days leave every two years for those big moments in your life like moving house or your birthday.
• Long-serving employees get a two week paid sabbatical after five years of service, then four weeks off after ten years of service.
• Private medical insurance through BUPA, that covers any pre-existing condition is a core benefit.
• A health cash plan that covers your everyday medical expenses.
• We offer a competitive salary based on your experience and the current market, plus the potential to earn an annual bonus based on performance.
• Access to tools to support your personal development on our dedicated learning platform.
• Support for your mental health with access to counselling.
• We match what you put into your pension up to five per cent.
• Pass on a tax-free sum that's four times your basic salary with our life assurance policy, with the option to increase it to ten times through our flexible benefit scheme.
• Our salary sacrifice car scheme gives you the option to buy a brand new, fully insured, and maintained car for a convenient fixed monthly amount taken from your gross salary (after 6 months service).
• Our flexible benefits scheme gives you an allocated amount to use each year on benefits like critical illness cover, dental insurance, travel insurance, or a gym membership.

Ready to join us and drive our success as a high-performing team? Simply Business is committed to providing equality and opportunities for all employees and candidates considering a career with us. We offer a workplace where colleagues are treated with respect and dignity. We don’t (and won’t) discriminate either directly or indirectly on the grounds of race, colour, religion, belief, political opinion, disability, nationality, ethnic origin, sex, sexual orientation or relationship status at any stage of the hiring process or during the course of your employment.

Thank you for your interest in a career at Simply Business!