The director of the first filming block of Doctor Who Series 12 was revealed on the the @Ruther2 Twitter account.
According to the CV of the production designer for the portion of the filming block recently completed in South Africa, Jamie Stone is directing the block.
— Ruther (@Ruther2) February 14, 2019
Two members of the crew working in South Africa, a script supervisor and a camera operator, are listed as working on the first and fifth episode of Doctor Who Series 12. It is very likely that Jamie Stone’s filming block consists of these two episodes.
After the South Africa location filming, more of Stone’s Block 1 filming continued on location in Cardiff.
Jamie Stone previously directed the Doctor Who short, The Last Day, which was a prelude to the Doctor Who 50th Anniversary Special, The Day of the Doctor.