Sadly, millions of people educated in the UK over the past 40 years who were not taught about the use of English grammar at school are often unsure of themselves when writing and speaking.
However, it’s never too late to learn and a book I would recommend is Collins’ Good Grammar (available from Amazon and other stores) by Graham King.
Exceptionally well written, this book is very easy to read and understand, and many people will realise that they know more about grammar than they thought they did, even though grammar was not taught to them at school.
It’s quite an entertaining book and demonstrates what a beautiful and practical language English is.
Robert Zarywacz