  The light curve of the quasar OJ 287 extends from 1891 up today without major
gaps. Here we summarize the results of the 2005 - 2010 observing campaign. The
main results are the following: (1) The 2005 October optical outburst came at
the expected time, thus confirming the general relativistic precession in the
binary black hole system. This result disproved the model of a single black
hole system with accretion disk oscillations, as well as several toy models of
binaries without relativistic precession. In the latter models the main
outburst would have been a year later. (2) The nature of the radiation of the
2005 October outburst was expected to be bremsstrahlung from hot gas at the
temperature of $3\times 10^{5}$ $^{\circ}$K. This was confirmed by combined
ground based and ultraviolet observations using the XMM-Newton X-ray telescope.
(3) A secondary outburst of the same nature was expected at 2007 September 13.
Within the accuracy of observations (about 6 hours), it started at the correct
time. Thus the prediction was accurate at the same level as the prediction of
the return of Halley's comet in 1986. (4) Further synchrotron outbursts were
expected following the two bremsstrahlung outbursts. They came as scheduled
between 2007 October and 2009 December. (5) Due to the effect of the secondary
on the overall direction of the jet, the parsec scale jet was expected to
rotate in the sky by a large angle around and after 2009. This rotation may
have been seen at high frequency radio observations. OJ 287 binary black hole
system is currently our best laboratory for testing theories of gravitation.
Using OJ 287, the correctness of General Relativity has now been demonstrated
at higher order than has been possible using the binary pulsars.
