for 50 years three generations of Macfarlanes have been postmen to the inhabitants of the tiny islands in Loch Lomond.

The milestone was marked yesterday with a new Royal Mail pennant to fly from the little wooden boat, the Lady Jean, which started the service in 1948 and still sails to each of the 38 islands dotted around the loch.

The original flag was presented to Alexander Macfarlane on his first trip. The new one was welcomed by Mr Macfarlane's 32-year-old grandson, Sandy, who operates out of his Balmaha-based boatyard.

''This has been a family tradition and one I'm delighted to carry on,'' said Mr Macfarlane, adding that the Lady Jean was still in excellent condition.

The loch, however, can turn from mill-pond calm to

heavy-going in a matter of minutes on the 10-mile round trip. In February 1963 it froze over, but Mr Macfarlane's grandfather and father, Barry, still got the mail through, by going on foot. And for all the privations, there are also obvious compensations.

''The route itself must be one of the most beautiful postal rounds in the country,'' said Mr Macfarlane.

Reflecting on half a century of Macfarlane postmen, he said: ''The mailbag is the only thing that's really changed.

''Everything is just like my grandfather and father did or worked with, right down to our coveted Royal Mail pennant.''