Why a Senior Independent Director is a key appointment for boardrooms
Warren Partners
The SID role is required in many UK companies but often poorly understood, says Warren Partners’ Laurence Vallaeys. Done well, it can be a stabilising force, shaping governance, succession and shareholder trust.
Senior Independent Directors (SIDs) have become a cornerstone of UK corporate governance, yet their role remains one of the least clearly defined in the boardroom. The UK Corporate Governance Code requires all FTSE 350 companies to appoint one, positioning the SID as an impartial intermediary between the Chair and other directors, a leader of the Chair’s annual evaluation and an independent contact for shareholders.
Despite this, responsibilities vary widely. As the Institute of Directors notes, the SID is often a sounding board for the Chair and a bridge for other stakeholders. Board Agenda also observed that the role “offers a vital safety valve for governance” but is too often “under-utilised or misunderstood.”
Lisa Scenna, SID at Genuit plc, says: “It is a role that can be easily misunderstood. Some describe the SID as a sounding board, others as a ‘sweeper,’ and there are even those who suggest the role lies dormant until a moment of crisis.” The reality, as many experienced SIDs point out, is that each appointment is shaped by context. As Zarin Patel, SID at Pets at Home and Anglian Water, says: “My SID roles were all bespoke and handcrafted.”
At its best, the SID is a steadying influence – ensuring psychological safety within the board, acting as a trusted intermediary at pivotal moments and offering reassurance not just in crises but throughout the life of the board.
Bringing value at the heart of the boardroom
The most effective SIDs build strong relationships not only with the chair but across the entire board and investor base. “Great SIDs observe, engage and ask questions to ensure the board is the best version it can be,” said Scenna. “When there is a great relationship between the SID and the Chair, they can work together to leverage the talent of the combined board to drive better decision making.”
She adds: “I will often take the time to take soundings from other NEDs in between board meetings, always focusing on how and what the board can do, to do things better and in a more effective way.” A Bain study into effective boards found that one of the most important attributes for board leadership today is the ability to “see around corners” – spotting tension early and guiding constructive resolution before formal escalation. SIDs, by nature of their remit, are often the first to notice these undercurrents.
The SID also plays a critical role in shareholder engagement, though such interaction is often confined to times of difficulty. Experienced board leaders argue that proactive dialogue pays dividends: “I would encourage SIDs to meet with shareholders, such as investors, in quiet times and engage with them to build a goodwill bank,” says Patel. “It will help engagement when real issues come up.”
Lynne Weedall, SID at Dr Martens, agrees that the SID role is particularly key when the shareholders also sit in the boardroom. “This is where keeping your independent hat on can be challenging and you need to be comfortable calling things out,” she says.
There is evidence that combining the SID role with the remuneration committee chair position can further strengthen shareholder relationships. It brings more frequent and productive dialogue with stakeholders, helping boards anticipate concerns before they escalate. Market practice also suggests that appointing a SID from within the existing board is usually preferable. Internal candidates already understand the business, personalities and dynamics, particularly the relationship with the chair. Trust built over time is central to the SID’s effectiveness.
External appointments can inject a fresh perspective, but they carry risks. Building credibility and relationships quickly is essential and careful onboarding is required. Where diversity is limited or the board is dominated by first-time or over-stretched non-executives, the pool of credible internal candidates may be small. Given the SID is the natural stand-in should the Chair be incapacitated, appointing a full-time executive, such as a sitting CEO, is generally inadvisable. Boards should also weigh complementarity with the chair’s skills and style as a key selection criterion.
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The solitude of independence
Unlike audit or remuneration chairs, the SID operates without a formal committee structure – a solitude that is both a strength and a challenge. The position demands sound judgement, fluency with stakeholders and significant non-executive experience. Effective SIDs bring broad business perspective and the maturity to interpret board dynamics, navigate CEO transitions and engage constructively with activist investors. They must balance independence with diplomacy, moving seamlessly from confidential adviser to mediator, from sounding board to source of reassurance.
A particularly critical moment arises when the SID is asked to lead the appointment of a new chair, especially when internal candidates are in play. Liz McMeikan, Chair of Nichols plc and SID at McBride plc, says: “Being asked to lead this selection process is among the most challenging tasks faced as an NED. The SID must ensure the recruitment process is robust, impartial, and attuned to the organisation’s future needs – aligning the board on priorities not just of experience, but on leadership style, stakeholder orientation and the capacity to govern through complexity.”
A path – but not a straight line – to the chair
The role has become an important staging ground for women aspiring to chair positions. A 2025 report shows that 191 women serve as SIDs across the FTSE 350. Some see this as tokenism; others argue it reflects recognition of the relational, emotionally intelligent leadership styles the position demands.
The SID role is often seen as a stepping stone to the chair, but the progression is far from automatic. Catherine Bradley, former SID of Kingfisher plc and now Chair of Interactive Investor, says: “While being a SID is good preparation for the chair role, people should be sensitive to the fact that the two roles are fundamentally different. They are very definitely in a number two, supporting role and they empower the chair and the CEO. The chair leads the board.”
Yet SID experience alone is no guarantee of promotion. As McMeikan cautions, aspiring chairs must manage the inherent tension in holding the chair to account while being considered as a potential successor. “Be transparent and tell the chair of your ambitions to step up; express your interest at the right time and in the right way. Be aware that in that case you will not be able to lead the process of appointing a new chair, so take time to select a new SID.”
However, Weedall takes a differing view when it comes to succession, seeing a Committee Chair role as being better positioned for moving up to chair. “RemCo chair is particularly good preparation for a move to chair,” she says. “It’s better if the SID comes with no ambition for internal chair promotion, in order to avoid any conflict of interest.”
Ultimately, becoming a SID is to act an anchor for effective governance – not a proxy chair or a hidden power broker. In the right hands, it is a catalyst for cohesion, accountability and long-term strength. For boards planning succession, navigating transformation or managing internal friction, the SID may be the most influential presence in the room.