It has been dry and well it is autumn so it has let go of its leaves.

yes, lack of water is the likeliest explanation - its been the dryest September for many years.

Have you had a frost too? that would encourage leaf fall.

The leaves are rapidly falling from our rowans, Agnes, it is simply that time of year.

Thanks all
Still think somrthing not quite right.

Does the tree otherwise seem healthy, that is, the bark, trunk, branches and twigs? No evidence of infestation or disease, or any exudate anywhere? Any sign of 'shepherd's crook' drooping on the upper or top stems? Was there any symptom on the leaves other than a change of colour before they fell? Was the change of colour what you'd expect, or did the leaves suddenly all go brown and crispy, or brown and soggy and droopy, or did the tree look as if it had been burnt before they fell?