It is understood the sacked men are traders Paul White and Neil Danziger, investment adviser Andrew Hamilton and Tan Chi Min, who used to work for RBS in Singapore.
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The annual event has earned a place in the record books ahead of the grand final of the 60th anniversary show in Austria this evening.
Local authorities said the move is necessary to "avert the growing number of deaths and increasing harm linked to psychoactive substances".
Some students argued that the centuries-old tradition of wearing gowns, suits and mortarboards to exams was 'archaic' and looked elitist.