This unusual X-ray transient was discovered in 1994 and showed a remarkable series of outbursts finally ceasing in 1997. It gained considerable notoriety in its first outburst by ejecting collimated relativistic jets at an estimated speed of 92 per cent of the speed of light. It is believed to contain an F5 subgiant star orbiting a 6-7 Solar mass black hole. The orbital inclination is quite high (around 70 degrees) and partial eclipses probably occur, at least during outburst.