JKR's cryptic answer. Who sent the Lestranges to the Longbottoms?

[potioncat]

No: HPFGUIDX 119847


 
> Annemehr:
snip 
LV already knew Crouch Jr. was a DE, of course, and the first item 
of information is what told him that Jr. was faithful.  Thus, Bertha 
need not know anything more than "she should."


Potioncat:
Also, as everyone thought Barty Jr. was dead, he could easily take 
over as Moody.  No one would miss him or think of him and LV didn't 
have to get anyone out of prison or confide in anyone else.  And 
Barty, more than any other DE, needed LV.