Senior Software Engineer in London

Job DescriptionAbout The Role

FDM is a global business and technology consultancy seeking a Senior Software Engineer to work for our client within the defence and security technology sector. This is initially a 12-month contract with very good prospects to extend and will be a hybrid role based in London with a requirement to attend the office at least one day per week and with up to two days’ notice when required.

Our client is a UK based technology company delivering secure unified communications and information sharing platforms for security and defence users. The role will support development across their existing secure communications platform as well as a new AI enabled decision support product. This is a senior position suited to an engineer who can work with a high degree of autonomy, contribute to technical direction and support less experienced engineers within a small, highly capable team operating in a secure environment.

Responsibilities:

• Designing, developing and maintaining features across secure communications and decision support platforms
• Building and maintaining backend services using C# and related technologies
• Developing and enhancing user interfaces using React
• Contributing to security focused system design when working with highly sensitive data
• Taking ownership of work items, collaborating closely with engineers, product specialists and stakeholders and, at senior level, contributing to mentoring and technical discussions

About You

• Strong commercial experience in backend development using C# and the .NET ecosystem
• Frontend development experience using React or a similar modern JavaScript framework
• Solid understanding of software engineering fundamentals and agile delivery practices
• Experience working in live production environments, ideally within regulated, government or secure systems
• Eligibility for BPSS clearance and preferably SC clearance or willingness to undergo SC clearance
• Minimum of 5 years’ experience in a software engineering role

About Us

FDM is an award-winning global leader in tech and business talent solutions, backed by more than 35 years of industry experience. We have centres across Europe, North America, and Asia-Pacific, and a global workforce of over 2500 employees. FDM has shown exponential growth throughout the years, firmly establishing itself as an award-winning employer, currently listed on the FTSE4Good Index and as a 2026 Financial Times UK ‘Best Employer’.

and Inclusion

FDM Group is an equal opportunity employer, and all qualified applicants will receive consideration for employment without regard to race, , , , , origin, , disability, veteran status or any other status protected by federal, provincial or local laws.

Why join us

• Career coaching, mentoring and access to upskilling throughout your entire FDM career
• Assignments with global companies and opportunities to work abroad
• Opportunity to re-skill and up-skill into new areas, develop non-linear career paths and build a skillset within your field
• Annual leave and work-place pension