My history teacher is awful: he begins talking of a topic, and then he starts digressing, and I think not even he realizes what he had explained.

After digressing, he returned to the subject.

The digression is escalating more and more.

If you'll pardon my digression, I'd like to relate a little anecdote that will help me to prove my point.

Ziri is digressing.

But I digress.

You digress!

I'm sorry, I digress.