Another of our Fruit Trees

Today’s blip is of the fruit on another of our fruit trees, but I am not quite sure what these are; Mrs GOG thinks they are greengages.  This tree was planted more than 40 years ago by the previous owners of the house and we have never eaten the fruit from it or properly identified it.  This year it has a bumper crop and I guess it is about time that we found out what it was, any suggestions?
 
Another day of doing very little and feeling completely washed-out, although I did watch, with interest, the Formula One.