Take a longshank hook size 10 (e.g Hayabusa Fly 376) and catch in a pair of bead chain eyes - 2mm as near to the hook eye as possible using figure of eight wraps. These are red bead chain eyes from B&Q of all places.
Dub a thorax of dubbed marabou from the position where the wire finished to a place just behind the eyes. Make sure you return the thread to the start of the dubbed thorax (Furthest away from the eyes).
Now for the tricky bit. Part the marabou fibres into two halves and pull the Pheasant tail fibres back through where they are parted. Secure the pheasant tail fibres with thread, whip finish and tie off, trimming any waste. (The thread is not finished at the eyes for this fly but whip finished at the start of the thorax).