I ride round that roundabout regularly and I find it's more about the planning than any particular bravery, at least in east->west and west->east directions. Great Eastern St itself is imo worse: two narrow lanes, many drivers want to overtake at inappropriate speed and without leaving any space, and taxis/minicabs often stop in the left hand lane to let passengers in or out.
Approaching from the east, the bus lane means that many drivers who want to turn left are in the wrong lane to do so and will left hook you if given a chance - get well ahead in the ASL and start off as soon as you see amber.
Approaching from the west, ignore the ASL feeder lane and stay in the left-hand traffic lane. The feeder is narrow, bends to the left, and places the cyclist next to a tall concrete kerb with a railing above it. It should be removed or made about 3x as wide, but in the meantime just don't go there. The lights in this direction are timed so that if you set off on green when entering the roundabout, the lights controlling the southbound entrance will also turn green as you approach them