What is a trustee?
A trustee holds and manages trust assets for the beneficiaries. Trustees owe fiduciary duties: to act in the beneficiaries' interests, follow the trust deed, invest prudently, keep proper accounts, and avoid conflicts. They are personally liable for breaches of trust.
The Trustee Act 2000 imposes a statutory duty of care, requires trustees to apply standard investment criteria, and requires them to take and consider proper advice on investments unless it is reasonable not to. Delegating the work does not delegate the responsibility.
Two or more trustees are needed to give a valid receipt for the proceeds of land, which is why trusts holding property almost always have at least two.
The practical burden is records: trust accounts, tax returns, Trust Registration Service entries kept current, and a clear file explaining why discretionary decisions were made. Trusts that fail do so through administration, not through drafting.