8 
7 6
5
4
3
2 
a 
b 
c 
d 
e f g 1 h ←→ to step through moves · Home / End — first / last Source
Why it works
In the Jobava London (with 2.Nc3) Black often develops 'by template' with 3...Nc6, missing how White's knight on c3 changes the picture. After 4.Nb5! the c7 square is set up for a king-rook fork. Black cannot defend c7 — the knight on c6 doesn't cover the square, the queen on d8 is blocked by its own diagonal, and the pawn kick 4...a6 doesn't help because 5.Nxc7+ still works. After Kd7 Nxa8 White wins the rook.
Refutation
3...e6 — calm consolidation defends c7 indirectly through the queen on d8 (after Nb5 there is no Nxc7+ threat because the f8 bishop will develop and c7 will be controlled). Alternative: 3...a6 (preemptively kicking Nb5), though that's passive.