What to do when Grievances are over 3 yrs old?

Hi All,

An employee during his disciplinary has also lodged a grievance. (He has since been dimissed and is appealing against the decision/process)

This grievance letter was received via a solicitor and is three pages long with points going back as far as 3 years. Some of the people on this list have since left the company. We are being asked to treat every single point as a separate grievance.