In Chapter 43-44, what dangers do Herbert and Pip realize Magwitch is in?Is there proof?

In chapter 43, Pip has just heard Provis’ story. Provis,
of course, is Magwitch, Pip’s erstwhile convict and current benefactor. Pip has
nicknamed him Provis to protect his identity. Pip and Herbert are afraid that Magwitch's
(Provis')  fellow convict and mortal enemy, Compeyson, will learn that he has returned
to London and seek to kill him. Of course, we later find out that this is true. For
proof, Pip says:

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If Compeyson were alive and should discover his
return, I could hardly doubt the
consequence.

Pip and Herbert
are also afraid that Provis (Magwitch) will be discovered by the authorities. He has
been forbidden ever to return to England and if he does, he will be arrested
immediately. So, Pip and Herbert hide him in an apartment separate from their own. At
the end of chapter 44, Pip returns to London after meeting with Miss Havisham and
Estella and telling them that he has discovered his benefactor’s identity. At the entry
gate to the city, the guard gives Pip a note from Wemmick that warns him not to go home,
so something is amiss!