Transit visa - flying to the UK from South Africa via Dubai

by Salome
(South Afrca)

I am south African and flying to the UK from South Africa via Dubai. Dates and times - 10th October leave SA 2:10pm and arrive in Dubai at 00:10am, depart Dubai 2:30am arrive UK 7am.
Depart UK 25th October 5pm, arrive Dubai 2:50am, depart Dubai 10:15am, arrive SA 4:25pm.
What are the visa requirements?