Rhianna is quite right as usual, if this is a sustained level, as noted on a number of occasions over a prolonged period or confirmed by a 24 hour BP monitor, it is well into the treatment range.
If your father has any other concomitant disease, such as diabetes
or raised cholesterol
then treatment will be even more important as risk factors are cumulative.
If he is attending any GP treatment will inevitably follow to comply with guidelines for BP management, which are both nationally and internationally accepted.
The aim would be to bring his BP down to no more than 125/85, less if he has other disease. In USA some specialists advocate even lower treatment targets.
The concept that 'normal' blood pressure rises with age has been quite rightly long abandoned as unsafe and unsound, since there is a direct relationship between rising BP and increasing stroke
and heart attack