Mainframe Application Developer & Support Engineer (COBOL)
We are seeking a skilled Mainframe Application Developer & Support Engineer to provide application support, troubleshooting, and ongoing enhancements within a mission-critical environment. This role forms part of a 24/7 service supporting high-availability Command-and-Control systems, requiring strong mainframe expertise and the ability to work on-site several days per week.
You’ll be responsible for day-to-day issue resolution, analysing system interfaces, developing enhancements, and ensuring the stability of core services. This is a hands-on, technically demanding role suited to someone with strong COBOL and mainframe experience who enjoys problem-solving in a service delivery environment.
Key Responsibilities:
Provide day-to-day support for mainframe applications in a mission-critical environment.
Diagnose and resolve technical problems affecting system operations and end users.
Analyse and troubleshoot issues across multiple system interfaces.
Develop software enhancements, new functionality, and system improvements as required.
Apply technical judgement to ensure changes do not impact operational stability.
Collaborate closely with stakeholders and communicate effectively with end users.
Participate in an out-of-hours on-call rota to support 24x7 system availability.
Maintain clear documentation and contribute to service delivery best practice.
Qualifications-
Essential:
Strong experience in Application Support, ideally within mainframe environments.
Proficiency in COBOL development and mainframe tools.
Experience with:
OS2200 mainframe systems
DMS (hierarchical) and/or RDMS (relational) databases
Transaction Processing environments (TIP/HVTIP or similar)
Ability to diagnose complex technical issues and deliver stable solutions.
Experience operating within a structured service delivery framework, ideally ITIL-aligned.
Strong interpersonal and communication skills for regular client interaction.
Willingness to work on-site several days per week and take part in 24/7 on-call cover.
Desirable:
Previous experience working with public sector clients.
Broader experience in enterprise-scale application support environments.
Familiarity with mission-critical, high-availability systems.
Why Join Us:
Opportunity to work on highly critical systems with real-world impact.
Collaborative and supportive environment with exposure to a wide range of technologies.
Professional development opportunities, including training in legacy and modern mainframe tooling.
Work alongside experienced engineers and specialists in a stable, long-standing service operation.
Competitive compensation package with strong benefits and career growth potential.
Important Information:
Due to the nature of the work, candidates must meet the eligibility requirements for CTC (Counter Terrorist Check) clearance, including a minimum of three years’ continuous UK residency. This requirement is mandatory.