  The quasar 3C 286, a well-known calibrator source in radio astronomy, was
found to exhibit exceptional multiwavelength properties. Its rich and complex
optical emission-line spectrum revealed its narrow-line Seyfert 1 (NLS1)
nature. Given its strong radio emission, this makes 3C 286 one of the
radio-loudest NLS1 galaxies known to date. 3C 286 is also one of very few known
compact steep-spectrum (CSS) sources detected in the gamma-ray regime.
Observations in the X-ray regime, rarely carried out so far, revealed evidence
for variability, raising the question if driven by the accretion disk or jet.
3C 286 is also well known for its damped Lyman alpha system from an intervening
absorber at z = 0.692, triggering a search for the corresponding X-ray
absorption along the line-of-sight. Here, we present new observations in the
radio, X-ray, optical and UV band. The nature of the X-ray variability is
addressed. Spectral evidence suggests that it is primarily driven by the
accretion disk (not the jet), and the X-ray spectrum is well fit by a powerlaw
plus soft excess model. The radio flux density and polarization remain constant
at the Effelsberg telescope resolution, reconfirming the use of 3C 286 as radio
calibrator. The amount of reddening/absorption along the line-of-sight
{\em{intrinsic}} to 3C 286 is rigorously assessed. None is found, validating
the derivation of a high Eddington ratio (L/L-Edd ~ 1) and of the very high
radio-loudness index of 3C 286. Based on the first deep Chandra image of 3C
286, tentative evidence for hard X-ray emission from the SW radio lobe is
reported. A large variety of models for the gamma-ray emission of 3C 286 is
briefly discussed.
