He came top of the class

It is not a good sentence.(Let us know the full context. It might make sense in a paragraph.)

You can say:

He was top of the class.

It means that he was the best student in his class.

AlpheccaStarsLet us know the full context. It might make sense in a paragraph.

Sorry found it in a dictionary 'oxfordlearnersdictionaries.com'

MustAskSorry found it in a dictionary 'oxfordlearnersdictionaries.com'

It does sound very British. In American English it is a bit short.

It would be OK in the context of describing a remarkable employee.

He was phenomenal. He came (to us as) top of the class (at Oxford.) He rose to be vice president in five years.

AlpheccaStarsIt does sound very British.

Yes, it is common in British usage. "He's a clever chap. He came top of the class."