Accountability
The Caldicott Guardian role was originally conceived as an advisory role, and to an extent it still is, though Guardians are accountable for any advice given. In practice, many information sharing and disclosure scenarios are decided by the Caldicott Guardian, and it is important that both advice offered and decisions are contemporaneously documented.
Where the Caldicott Guardian is a director or member of the board or governing body, they will most likely already be accountable directly to the chief executive or chair of the organisation. Where this is not the case, or the individual is not a member of the senior management team, direct accountability to the chief executive may still be the most appropriate option, although accountability to a senior executive may be appropriate in some organisations. Either way, the Caldicott Guardian must be able to speak independently to those in charge of the organisation.
Accountability to the SIRO is not recommended, on the grounds that the SIRO might then overrule the Caldicott Guardian. They should have a relationship of mutual respect and ideally they should be of equal seniority. However, it is the good relationship and the ability to work transparently through potential conflicts of interest that matters more than the detail of who does what.