  In lattice QCD, colour confinement manifests in flux tubes. We compute in
detail the quark-antiquark flux tube for pure gauge SU(3) dimension $D=3+1$ for
quark-antiquark distances R ranging from 0.4 fm to 1.4 fm. To increase the
signal over noise ratio, we apply the improved multihit and extended smearing
techniques. We detail the gauge invariant squared components of the colour
electric and colour magnetic fields both in the mediator plane between the
static quark and static antiquark and in the planes of the sources. We fit the
field densities with appropriate ansatze and we observe the screening of the
colour fields in all studied planes together with the quantum widening of the
flux tube in the mediator plane. All components squared of the colour fields
are non-vanishing and are consistent with a penetration length lambda ~ 0.22 to
0.24 fm and an effective screening mass mu ~ 0.9 to 0.8 GeV. The quantum
widening of the flux tube is well fitted with a logarithmic law in R.
