Did the Brits actually send...
... a hysterical hyper emotional wreck with adhd diagnose? As a first person in space?
Maybe a rhesus monkey did have a greater chance of making it, it would never have spoken to the Russians.
The astronaut 'Guy Taylor" is suffering from severe Hypoxia (Oxygen starvation). Three of the main symptoms of this are confusion, disorientation and acute behavioural change. Brain function can become impaired making is difficult to pay attention, making irrational decisions with poor judgment. After consultation the production team decided to go with these traits of the illness for the character from the moment he wakes up after blacking out. Taking him out of the environment he would normally have complete control of during his test pilot days and throwing him into an environment with little to no oxygen and see his character change from the consummate professional to someone barely holding it together on to the edge of his life.
Hypoxia can also cause severe headaches and hallucinations, seeing and believing things are real that aren't there.