  The light curve of quasar OJ287 extends from 1891 up today without major
gaps. This is partly due to extensive studies of historical plate archives by
Rene Hudec and associates, and partly due to several observing campaigns in
recent times. Here we summarize the results of the 2005 - 2010 observing
campaign, in which several hundred scientists and amateur astronomers took
part. 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. At the same time, 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. (2) The
nature of the radiation of the 2005 October outburst was expected to be
bremsstrahlung from hot gas at a temperature of 3 10^5 degrees 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 the observations (about 6
hours), it started at the correct time. Due to the bremsstrahlung nature of the
outburst, the radiation was unpolarized, as expected. (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 is
expected to rotate in the sky by a large angle, which has been confirmed. The
OJ287 binary black hole system is currently our best laboratory for testing
theories of gravitation. Using OJ287, the correctness of General Relativity has
now been demonstrated up to the second Post-Newtonian order, higher than has
been possible using binary pulsars.
