If White attempts to mate by guarding e7 to threaten 2.d7 Black has adequate defences – 1.Rae5? Rd2! and 1.Rhe5? Bg4!
The key is 1.Kg7, threatening 2.Bf7 mate, giving two variations where White must make a careful choice of rook move to e5 to leave a Nowotny interference on move 3.
1...Rf2 2.Rae5 (threat 3.d7) Bg4 3.Rhf5 threats 4.d7 and Bf7
1...Bb3 2.Rhe5 (threat 3.d7) Rd2 3.Rad5 threats 4.d7 and Bf7
After 1...Bd4+ both 2.Rae5 and 2.Rhe5 mate on the fourth move. The b6 bishop is necessary to prevent a cook by 1.d7+ Kxe7 2.d8Q+ etc.
Dafydd Johnston: I like the logic of White’s move order, holding the rooks back for one Nowotny or
the other. Pity about the dual after the check, but I suppose it is inevitable.