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 ResponsibilitiesDevelop and maintain Windows applications using C#/.NETContribute to secure communications software, including WCF-based componentsReview, understand, and reverse engineer existing code where documentation may be limitedWork within a formal software development lifecycle (requirements, design, implementation, verification, compliance)Participate in design reviews and technical discussionsCollaborate with other engineers using iterative / Agile-style developmentEnsure software meets quality, safety, and user expectationsEssential Skills and ExperienceStrong professional experience in C# and .NETWorking knowledge of C++ (reading and understanding existing code)Experience with Windows Communication Foundation (WCF)Proven ability to investigate and understand legacy or in-flight codebasesFamiliarity with software