The Imerys UK Pension Fund has appointed Aon as fiduciary manager for its £550m scheme.
The scheme - sponsored by industrial minerals specialist Imerys Minerals - has nearly 5,900 members.
Aon is actuary to the Imerys Scheme and has provided it with investment advice for well over a decade. In its new fiduciary management role, Aon will now provide implementation services alongside investment advice, including journey planning, to help the scheme trustees continue to make better decisions.
Aon was selected following a competitive tender process.
Imerys UK Pension Scheme trustee chair Edwin Bruce-Gardner said: "As trustee to the Imerys Scheme, we had eight investment managers and it became clear that the time and resources required to effect a dynamic investment policy without an in-house investment team was becoming more and more onerous in a world of increasing regulation and investment risk. We therefore required greater investment expertise.
"Fiduciary management was a natural progression. After presentations on different approaches from several fiduciary managers, we decided to stay with Aon, which has successfully advised us for many years and which we considered to be the best fit."
Bruce-Gardner said Aon's approach was a continuation of the diversified and liquid policy previously adopted by the trustee to meet its investment goals, but with Aon taking over all the day-to-day management decisions - something that left the trustee with more time to concentrate on other matters.
He explained: "The new approach gives us access to a wide range of investment options, along with the speed and nimbleness to respond quickly to changes in market conditions and to evolve as we approach full funding. The trustee has full confidence that Aon will be successful in meeting the trustee's objectives."
Aon head of UK investment Maria Johannessen added: "We have worked with the Imerys Scheme for over a decade and it's great news that we can capitalise on the understanding of the scheme's needs and objectives that we have built up over that time.
"Our aim is to provide more certainty, lessen the decision-making burden and provide better value to the scheme. All this will also ensure continuity and stability for members and allow the scheme to navigate new forms of volatility with confidence."