Suitable calibre for Lion?

[Heym SR20]

I am in the process of renewing my FAC and have added a .375H&H mag to the wish list.
I predominantly wanted a double rifle for Boar, but have just had the spark of an idea to visit Africa for hunting rather than work!
I am beginning to get the idea of taking a lion as a once in a lifetime experience.
Would a .375 H&H mag be enough gun or do I need to look for something bigger?
Any advice gratefully received.

Boddington recommends 375 or a 416 in The Other Dangerous Game

Only time I have been involved in chasing a Lion I had an old rattley 12 bore with slugs in each barrel. I did get a chance at a shot thank heavens!