The law places an obligation on all of us to care for the wellbeing of others. This is often referred to a duty of care to others. For tree owners this means that you have a duty to care for anyone you can foresee entering your property (invited or not) or anyone using any neighbouring property. To meet their legal obligations tree owners should conduct regular inspections of their trees. The law does not dictate how often the inspection should be made or on what format but the level of inspection does depend on who the tree owner is. Householders can have a much more informal arrangement than a large estate.
If you own a tree it should be inspected on a regular basis, however this inspection could be carried out by the home owner. If it is a tree in your garden you will notice any changes (early left loss, die back, fungal brackets, etc) and can call in a tree surgeon for advice if needed. You may also have a tree surgeon (arborist) doing work or quoting and he can cast his eye over all your trees. By informally monitoring your trees this way you have gone someway to meeting your duty of care and may not need to do anything further. If you have a large number of trees you may wish to call in an arborist to conduct a written tree condition survey (also called a tree risk survey) every 18-36 months or as deemed appropriate.