  In the reaction e+e- -> WW -> (q_1 qbar_2)(q_3 qbar_4) the usual
hadronization models treat the colour singlets q_1 qbar_2 and q_3 qbar_4 coming
from two W bosons independently. However, since the final state partons may
coexist in space and time, cross-talk between the two evolving hadronic systems
may be possible during fragmentation through soft gluon exchange. This effect
is known as Colour Reconnection. In this article the results of the
investigation of Colour Reconnection effects in fully hadronic decays of W
pairs in DELPHI at LEP are presented. Two complementary analyses were
performed, studying the particle flow between jets and W mass estimators, with
negligible correlation between them, and the results were combined and compared
to models. In the framework of the SK-I model, the value for its kappa
parameter most compatible with the data was found to be: kappa_{SK-I} =
2.2^{+2.5}_{-1.3} corresponding to the probability of reconnection P_{reco} to
be in the range 0.31 < P_{reco} < 0.68 at 68% confidence level with its best
value at 0.52.
