I was expecting the worst this morning as a thick layer of snow was covering just about everything. In fact, the journey was less eventful than I feared - RER E to Haussmann St Lazare and then a direct train to La Defense.
I was actually rather hoping that the train would stop at Bécon (I boarded it too late to see where it was going) but it didn't.
In fact, the walk back from La Défense to the office is not long at all - around 25 minutes, but it must be more pleasant when there is no snow and ice.
Total journey time = 75 minutes
No problems on the return trip, although all sorts of dire warnings had been issued about delays and cancellations due to the extreme weather.