There are some toadstools growing in the lawn.  I'm going to measure their progress during the day.  At  9.50 this morning they are already visibly taller than when I first went out and spotted them at 8.30am.  They are 5.5cm tall and have developed a distinctive stalk and white cap.  This morning they appeared as a white blob.  Wish I had a camera.  Must buy a camaera...