Radio Monique (Later Radio 558) was an offshore radio station part financed by the Canadian Lottery 6/49, broadcasting to Holland from the Radio Caroline ship, Ross Revenge.

Originally intended to broadcast in 1981 from a new radio ship called mv Magda Maria alongside a station to be called Radio Paradise (No relation to Radio Paradise), this arrangement fell through and Radio Paradise never did make it to air, but for some test transmissions. On the way over to Europe the ship lost part of its aerial. Shortly after commencing tests, the Dutch navy towed the ship away. Monique however entered into an agreement with Ronan O'Rahilly of Radio Caroline to rent time on Caroline from October 1984. In fact, following antenna problems, the station began test transmissions on 15 December 1984 and commenced full programming at midday the following day on 963 kHz. Radio Caroline had broadcast for over a year from the Ross Revenge but failed to attract enough advertising to be able to continue alone.

It has been suggested that Monique's relationship with Caroline was originally intended to be temporary. The station provided some technical and tendering assistance to Caroline's rival Laser 558, and it has been rumoured that Monique was considering moving its base of operations to the Laser ship MV Communicator. If so, then the unexpected closure of Laser in 1985 put paid to the plan. Another suggestion is that the Laser operation was aimed at silencing any possible competition. See blank">http://www.adroberts.net/ for details. Ad Roberts was a presenter on Monique at the time.

In October 1987 Radio Monique was sold and a month later moved to 819 kHz. This move was necessary because Finland had started up a new 600 kW transmitter on 963 kHz. Shortly after, during a storm on 25 November 1987, the aerial mast broke on board the Ross Revenge. Caroline returned fairly quickly with a makeshift aerial but was initially unable to offer Monique a sufficient quality service. During the break Radio Monique became Radio 558 and in May 1988 returned on 558 kHz. Later the station made one more final move, this time to 819 kHz, and again changed its name accordingly.

On August 19, 1989 representatives of Britain's _Department of Trade and Industry their counterparts from the Netherlands Radio Regulatory Authority raided the Ross Revenge during the course of which equipment was wrecked or confiscated. It was claimed that Caroline's use of a short wave frequency 6215 kHz for the transmission of paid-for religious programmes was causing interference to maritime communications (although the shortwave transmissions had stopped on the day prior to the raid) but another possible reason for the raid was that Radio 819 was running cigarette adverts, a product banned from being advertised by European Union law. From the Dutch point-of-view however, the main reason was that 1.5 million people a day were listening to 819. No evidence of these audience figures can be found.

Part of the raid was broadcast live before officials finally cut off the transmitters. Dutch staff were arrested and taken back to the Netherlands, together with most of the broadcasting equipment. This included all studio equipment and most transmitter components. The transmitter used for Caroline was extensively damaged and is still beyond repair. The 50 kW transmitter used for Monique has been restored for display purposes after most of its parts had been handed back to radio Caroline after the offshore era. Caroline staff were not arrested and were left on the ship and Radio Caroline later recommenced broadcasts. Attempts were made to return Monique/819 to the air, but were unsuccessful. The supporting organisation on land had been dismantled prior to the raid on the ship.