CONTROVERSIAL he may be, but psychiatrist Dr Ng Man-lun (a.k.a. Dr Sex) is always entertaining. When he delivered his lecture on 'alternative marriage systems' to a hushed group of Hong Kong University undergraduates last week, he was ready to defend his theory to the end. Dr Ng's multi-modal marriage, or MMM,would legalise group marriage: a woman could collect a harem of four husbands, or equal numbers of husbands and wives could swap vows collectively. 'They say my proposal will encourage people to have multiple sexual partners,' said a grinning Dr Sex. 'But first, you must tell me that having multiple sexual partners is no good. At a buffet you can eat as much as you like, but you will only eat as much as you need.' Food for thought?