Saplings to an avenue of mature trees

Is it twenty or twenty five years?
Or is it more?
I do remember when these trees were first planted in Southfield Park in Acton.
They were little saplings then.
They survived because for the first five or more years of their time growing they remain quite bushy and vandals could not easily break the trees'  trunks.
So they survived and now amazingly all those years later form a great little avenue accross a good quarter of the part.
Living trees make cities!