Our client, a large organisation with over 5,000 staff, is urgently seeking a skilled and motivated Senior Network Infrastructure Engineer to join their Head Office team in Hertfordshire. This is an exciting opportunity for an experienced engineer with a strong background in network design and multi-site infrastructure, who is also comfortable working across on-premises server platforms and hybrid environments. You'll play a key role in designing, maintaining, and evolving our network and infrastructure, supporting our multi-office WAN environment. Your work will include managing routers, switches, firewalls, and SAN storage, as well as overseeing Windows Server, Active Directory, and VMware platforms. You'll be actively involved in the transition from current network to enterprise-grade network solutions such as Juniper, Cisco, or Fortinet, would be highly beneficial. This role also provides exposure to On-perm, Azure, Microsoft 365, and hybrid cloud technologies, but your main focus will be on network infrastructure, server environments, and WAN connectivity. You'll be responsible for planning, implementing, and optimising network designs to ensure reliability, performance, and scalability across multiple sites. We're looking for someone who is hands-on, technically curious, and project-focused, with a proven track record of delivering multi-office network infrastructure projects. Fortinet, Juniper, or Cisco certifications would be an advantage but are not essential. In return, you'll join a forward-thinking IT team where your expertise will have real impact, and you'll be supported to take ownership of complex challenges, drive continuous improvement, and contribute to the evolution of enterprise infrastructure. If you're passionate about network and infrastructure projects, enjoy solving technical challenges, and want to work with enterprise-grade systems across multiple sites, we'd love to hear from you. InterQuest Group is acting as an employment agency for this vacancy. InterQuest Group is an equal opportunities employer and we welcome applications from all suitably qualified persons regardless of age, disability, gender, religion/belief, race, marriage, civil partnership, pregnancy, maternity, sex or sexual orientation. Please make us aware if you require any reasonable adjustments throughout the recruitment process.