The company faces substantial capex requirements (ongoing network digitisation and expansion) and a leverage profile that is already stretched relative to typical investment‑grade regulated utilities (net debt/EBITDA around 5.5×). Rating headroom is limited, and preserving the investment‑grade rating will likely require optimisation of the capital structure. Issuing a hybrid bond would provide equity‑like credit, lowering adjusted debt and improving leverage metrics, while the cost of a hybrid would be marginal relative to the benefit of avoiding a downgrade. Therefore, a hybrid issuance of **11.25 %** of total adjusted capital is appropriate.

<answer>11.25%</answer>