There are plenty of foods that are by definition vegan, for example all vegetables and fruit. There are also a rapidly increasing range of foods that are labelled vegan specifically to help sell them to customers interested in vegan foods. However there are a lot of interesting foods that are vegan accidentally. Some of these have been around for a decades. As someone from the UK I here are some web pages listing listing foods for people living in the UK.
veganuary.com/starter-kit/a...
veganisingit.com/accidental...
veggieathletic.com/accident...
I am aware that the vegan society is trying to get better labelling. You should always check the ingredients list carefully. Also even that may not be enough. Almost every week some food seems to be on recall because it contains, say milk, and yet the ingredients list does not mention it.
There may be other more definitive lists. Do you know of any?
Take care!