Does Eurostar enforce any penalties for booking a throwaway return ticket?

Question

As outlined in a related question, Eurostar charges less money for short-term return trips than it does for one-way trips. Assuming one only needs a one-way ticket to/from the UK and buys a throwaway return ticket, can they expect any issues later on?

I'm mostly interested in how it works in practice, not what it says in their T&C.

Answer 1

Looking in my travel history, I found that I travelled from Brussels to London in Jan 2015 on a throwaway return (23 pounds cheaper) without going back.

Never heard anything from Eurostar since, so given that the question is about actual practice, no, at least in Jan 2015 they weren't enforcing any penalties.