Our Client based in Basildon are looking for an experienced Software Development Engineer to join a specialist engineering team delivering secure Windows-based software systems for safety-critical and defence-related applications. This is a Temporary position until April 2026 with the possibility of extension. This role would suit a self-motivated engineer who is comfortable joining a project mid-stream, investigating existing code, and contributing to the next phase of development within a structured software lifecycle. You will receive an initial onboarding period, followed by hybrid working with occasional on-site access to specialist test hardware. Key Responsibilities Develop and maintain Windows applications using C#/.NET Contribute to secure communications software, including WCF-based components Review, understand, and reverse engineer existing code where documentation may be limited Work within a formal software development lifecycle (requirements, design, implementation, verification, compliance) Participate in design reviews and technical discussions Collaborate with other engineers using iterative / Agile-style development Ensure software meets quality, safety, and user expectationsEssential Skills & Experience Strong professional experience in C# and .NET Working knowledge of C++ (reading and understanding existing code) Experience with Windows Communication Foundation (WCF) Proven ability to investigate...