About us

High-performing websites for organisations who value their digital assets

We are Castlegate, a specialist website development agency based in York, with a reputation reaching far beyond the city walls. Since the company was founded in 2011, we have consistently punched above our weight, building websites for global brands, household names, and national charities.

Over our three decades in business, we’ve honed our instincts, sharpened our skills, and built up a wealth of specialist expertise. Today, we are recognised as leaders in digital inclusion, corporate cybersecurity, custom-coded WordPress solutions, and high-performance websites.

But what truly sets us apart is our people. Every senior staff member is a subject matter expert with years of specialist experience. We assemble teams with the perfect mix of skills to ensure success.

Trusted by organisations that need a reliable website design and development partner

Our clients range from global organisations to local businesses with far-reaching impact. We’ve designed websites for high-profile charities, leading academic networks, cultural attractions, corporate giants, and the public sector.

Looking beyond differences in size or sector, they all share three key priorities:

They take their valuable digital assets seriously and trust us to keep them secure, stable, and future-proof.
They want a long-term website partner that is invested in their success and will help them achieve their goals.
They run business-critical websites. For them, downtime isn’t just inconvenient. It means lost income, missed opportunities, damaged reputation, and failed service users.

If this sounds like you, book a call to discuss how we can support your organisation too.

A collaborative process to achieve a shared vision

We take a consultative, strategic approach to every website project, asking questions to understand our clients priorities and ensure that every decision supports their goals.

Once we have a clear shared vision, we build to fit. Our expertise means that we’re not restrained by off-the-shelf solutions. Instead, we build custom coded websites to meet unique requirements.

By blending technical precision, creative thinking, and rigorous project management we deliver websites that routinely exceed our clients expectations and equip them to move into the future with confidence.

Our history

Jim Semlyen founded Semlyen IT Consultants in 2005, offering web development services to local businesses around York. Based in an office on Castlegate in the city centre, his friendly, personal approach and technical attention to detail meant the company quickly grew in size and reputation. In 2011, it became Castlegate IT Ltd and Jim was joined by Richard Lane and Andy Reading as company directors.

By 2015, the team had grown to include 12 talented designers, developers and project managers and we moved to a new, larger office on Walmgate. We are still proud to support businesses of all sizes around York, but we now have a range of national and international clients who value our dedication, honesty and high standards. The way we work hasn’t changed though: we care about our clients and we put the same attention to detail into every single project.

Our mission, values and goals

We’ve spent many years thinking carefully about the direction of Castlegate IT, the reasons behind what we do, and why.

We believe it’s important to understand our mission and values to ensure that our team aligns with our vision. It also allows our clients to gain a better understanding of who we are, and whether we’re a good fit.

Our ethical policy

When you work in the digital world, it’s easy to forget that what you do has an impact on the physical world. Castlegate IT is a responsible business and we pride ourselves on our honesty and integrity. Our ethical and environmental policy outlines our commitment to high standards of ethical behaviour, above and beyond our legal obligations.