london wayde van niekerk duly qualify world championship 400 meter final sunday defend champion world record holder look real battle hand sear semi-final performances south african desperately try conserve energy bid 200/400m double force go deep would like botswana baboloki thebe second three semi-finals eventually clock 44.22 second stage two 21-year-olds fire warn massive personal best steven gardiner improve bahamas national record go 44 second first time clock 43.89 might pay final tuesday nathon allen also set jamaican record take almost half second best 44.19. botswana isaac makwala look comfortable win heat 44.22 second van niekerk originally draw open heat organizers change lineup please south african whoever change thank ready 43 second say seem like every time go track someone break 44 second good competition mean always game try get round conservatively can american big hope fred kerley scrap final fast loser former olympic world champion lashawn merritt another man serve dope ban though unlike compatriot justin gatlin loudly cheer london crowd fail make van niekerk force work way tantalize 400m final