In reply to TeeBee:
A couple of years ago I decided to go to the Alps in the summer by train. I thought it would be an interesting and fun thing to do.
The first leg of my journey was by Eurostar and I had to put my ice axe, ice screws, knife and walking poles in registered luggage. The need to do this wasn't well advertised - I had to make enquiries in advance to find out I needed to do it. Eurostar does seem to apply the same thinking to luggage as a airplane and so I imagine this stuff would have been confiscated if I had just turned up with it in my bags.
I was told that Eurostar couldn't put my registered luggage on the same train as me and if I wanted to have my stuff in Paris when I arrived, I would have to put it on an earlier train. Obviously I wanted my stuff there at the same time as me as I needed to get a connecting train. This meant that I had to go to the Eurostar terminal the day before I was travelling so I could send my registered luggage on ahead of me. On the way back I had hand in my registered luggage, get my train to London and then go back to the Eurostar terminal the next day to collect my stuff.
If all this wasn't enough, the registered luggage place in Paris is pretty hard to find and seems to shut entirely if the staff are off dealing with luggage.
I get why Eurostar might not want people taking ice axes, etc on a train, but not being able to put the luggage on the same train as you is really unhelpful and puts me off getting Eurostar for Alpine trips. Hopefully this has now changed, but I'd recommend checking with them before turning up at the Eurostar terminal.