The present disclosure relates to subsea tool apparatus and methods, particularly but not exclusively tool apparatus and methods relating to subsea trees or so-called “Christmas trees”. The subsea tool is for reinstating the functionality of a subsea tree valve actuator, by applying a thrust force to the subsea tree valve actuator stem, characterised in that: the tool gets its power supply to provide load on the actuator stem, directly or indirectly from the subsea tree SCM (subsea control module) supply.