The 18th anniversary of anything is not one that usually draws crowds - even for an event as momentous as the massacre that followed the Tiananmen square protests in Beijing on June 4 1989.

But this year, the Hong Kong organisers of an annual Tiananmen vigil, the only public memorial to the event held within the People's Republic of China, have received a fillip from an unlikely person - the head of a pro-Beijing political party.