Police battered through a brick wall into a cannabis cafe whose owners had previously denied any drug connections yesterday.
The venue, which was designed with expensive furniture and trendy fittings, was secured with burglar bars on all windows and an air-lock double steel door, used in some defence bunkers.
Officers from Adur stormed the cafe, where 13 people were using the facilities, after reports of illegal drug taking on the premises - despite the recently introduced smoking ban in public places.
A furnace, which police believe may have been used to dispose of evidence, was found and was bellowing out smoke.
Three local men in their 30s were arrested for drug offences.
Drugs and hundreds of pounds of cash were found and police said they will be investigating whether drugs' profits were used to buy or fund the venue.
In February this year a spokesman for the social club, in Freshbrook Road, Lancing, denied the place was a haven for cannabis smokers.
Previous investigations by police have turned up no firm evidence of drug use on the premises.
Chief Inspector Lawrence Hobbs, of Sussex Police, speaking after the raid, said: "This operation had been planned over many months and is not targeting recreational cannabis users but those individuals who we suspect are concerned in the management of this cafe, which is operating illegally within the heart of a residential community.
"I would like to apologise to the members of the community who live nearby who perhaps feel we should have acted sooner but it has been necessary to prepare our investigation thoroughly before executing the warrant.
"Likewise, I would apologise to completely innocent members of the community who live nearby who may have been caught up in our attempts to disrupt the cafe and would have been stopped by police officers.
"This week the Government announced a review of the laws surrounding the use of cannabis and, whilst I cannot speculate on the outcome of the review, what I can say as a local police commander is that I am doing all that I can to suppress antisocial behaviour and criminality in the Lancing area and I am certain that there are established links with the use of cannabis."