I have just looked up the link Jalima and it was helpful but rather lengthy ! I have copied the tip which I think will help me and here it is. Thanks.
‘I hope this has helped and that you’re not past caring about the whole subject! Here’s a final hint: past is never a verb, so if you know that the word you want is a verb, passed is always the right choice. Conversely, if you need a noun, adjective, adverb, or preposition, it’s got to be past.’
Finally Jalima the owner of that dog you kindly looked after earlier this year, would definitely know the answers to all our queries. ?