What does "彼は必ず成功するに違いない" mean?


The following sentence is taken from Routledge's frequency dictionary of
Japanese:

> 彼は必ず成功するに違いない。

The translation goes as follows:

> He must always succeed.

Is this translation correct? I interpret this sentence as "He will certainly
succeed" or "I'm sure he will succeed" or something along those lines. If
Routledge's translation is correct, what am I misinterpreting?

