Between an hour and half and two hours. But over half an hour of that was waiting around until they checked everyone's paperwork (Photocopying passports etc). The actual test itself will take about 45 mins (9 mins for the reasoning, verbal and mechanical comprehension sections, and 16 mins for the numeracy section). RFA candidates will be allowed to go as soon as the test is over. Then they'll check and double check your results and forward them to the RFA recruitment office. Unfortunately you dont find out what your result is. You just receive a letter telling you whether or not you got the required score for the role you applied for.
Mine went the same way SuperNexus, I think everyone gets caught out by the time limit on the first section. I got through on my English as my maths is rusty. Fingers crossed and good luck to you, keep us posted.