Does anyone have any 'model' definitions for Force Majeure they could share?

Global and geo political events across the world are having ever increasing impacts on construction projects in the UK, sometimes with alarming consequences the extent of which can be impossible to accurately predict. At the outset of the Covid 19 pandemic Force Majeure had more ‘air time’ than i can ever previously recall but many contractors, often in desperation, were making claims under Force Majeure without giving much thought to how they would then be able to demonstrate a FM event let alone what it’s impact actually was.
There is no standard definition of Force Majeure in English Law and most standard forms of contract leave the matter to be dealt with in very subjective ways.
AS a compensation or relief event it is fair to say that FM will usually always be a last resort event, however contractors would be better protected if they could turn to a suitable model definition to include as a contract amendment.