Highly suited to former lawyers, and no formal retraining required. Company Secretaries for public companies are basically required to be either a lawyer, accountant, or possess the Institute qualification. Almost anyone can be a company secretary for a private company. A solicitor or barrister does not mandatorily need any re-qualification therefore, although adding the ICSA qualification is unlikely to be a disadvantage, and gives Chartererd Secretary status.
The ICSA is "the qualifying body for company secretaries and senior administrators, ICSA offers a professional qualification covering business, company law, corporate governance, management, finance/accounting, administration and company secretarial practice.". With a legal qualification, you can fast-track through the ICSA qualifying scheme "to a board-level role".
Sometimes you see the role of Company Secretary combined with that of General Counsel, and duties can be expected to include jurisdiction over regulatory compliance, corporate governance, liaising with auditors, pension scheme management, insurance matters, reporting to Directors, elements of risk management, preparing agenda and taking minutes etc. Every company needs one. Bigger companies advertise for 'Assistant Company Secretaries' in support of the Company Secretary and Company Solicitor or General Counsel. You can see some fairly big positions advertised in the Times law section on a Thursday.