There are two entries in the GTB for 20th April.
We have no Ainsleys in our family tree but when I search on Ancestry, there is a Wilhelmina Ainsley in the Yorkshire area in 1891 and 1901 census. I can also find a death certificate for this name in 1966. One of my mother's godmothers was always referred to as Willa. I wonder if this is the same person.
I assume this is Queen Elizabeth who was actually born on 21st April 1926. She was born in the same year as my mother (who also has an April birthday).
I'm a couple of days late in reporting this but I'll do my best to be on time with the next entry, on 24th April.