When my parents bought their last house in 1954 there were two fruit trees in the back garden. One was a very prolific pear, but the other, which was unknown, didn't bear any fruit for 3 or 4 years. My Dad said that it would be removed if it didn't fruit the following year.
Lo and behold, a bud blossomed and a solitary greengage subsequently appeared. It was a race between us and the birds as to who would benefit from this offering, which ended up in a dead heat shared 50 / 50 between us.
The tree was replaced the following season with an eating apple instead (which also didn't fruit very well !).