Are you a Lead Infrastructure Engineer ready to take ownership of a high-performing infrastructure team delivering secure, mission-critical services?Sopra Steria is delivering a major greenfield programme for the Defence sector, building and integrating infrastructure and applications within highly secure environments. This is a rare opportunity to lead technical delivery on a nationally significant programme where the work you do has real purpose, scale, and impact.We are looking for an experienced Lead Infrastructure Engineer to oversee the day-to-day technical operations of the Windows infrastructure team, reporting to the Head of Operating Systems. You will combine hands-on technical expertise with people leadership, helping to shape team capability, improve service quality, and ensure the successful delivery of infrastructure services and project outcomes.This role would suit someone with strong Wintel and VMware experience, ideally gained within Defence, MoD, government, or similarly secure and regulated environments.This role is full time on site in the Hertfordshire area.What you will be doing:Lead, manage, and mentor the Windows infrastructure team, building capability and developing a strong SME structure.Oversee day-to-day technical operations, ensuring services are delivered in line with SLAs, governance, and security requirements.Support project delivery across solution design, estimation, detailed design, implementation, and service transition.Provide technical