Complex sentence: Travelling to Istanbul, Bond heads into the city to meet with station head Ali Kerim Bey, during which he is tailed from the airport by Bulgarians working for the Russians, who are in turn tailed by Grant.
Split into simpler sentences: Travelling to Istanbul, Bond heads into the city to meet with station head Ali Kerim Bey. While travelling into the city, Bond is tailed from the airport by Bulgarians working for the Russians, who are in turn tailed by Grant.