Ann participated in a 20 km fun walk/run in London. Ann took two rest breaks during the walk/run. The graph below shows the distance covered by Ann against the time taken by her to complete the event:

The race starts at 08:00. One hour later is 09:00.

At 09:00, the distance covered is $4 \text{ km}$.
Ann walked $\boxed{4 \text{ km}}$ in the first hour.

2.4.2)

The first horizontal segment is from 09:30 to 09:45.
The second horizontal segment is from 10:45 to 11:00.
Ann took her rest breaks from $\boxed{09:30 \text{ to } 09:45}$ and from $\boxed{10:45 \text{ to } 11:00}$.

2.4.3)

Duration = $09:45 - 09:30 = 15 \text{ minutes}$.

Duration = $11:00 - 10:45 = 15 \text{ minutes}$.
Each rest break lasted $\boxed{15 \text{ minutes}}$.

2.4.4)

The graph line crosses $12 \text{ km}$ between 11:15 and 11:30. It appears to be exactly halfway.
Ann reached the $12 \text{ km}$ mark at approximately $\boxed{11:22:30}$ or $\boxed{11:23}$.

2.4.5)

At 10:00, the distance covered is $7 \text{ km}$.
Ann had walked $\boxed{7 \text{ km}}$ by 10:00.

2.4.6)

The race is $20 \text{ km}$.

The graph ends at $20 \text{ km}$ at 12:00.

Start time = 08:00. Finish time = 12:00.
Total time = $12:00 - 08:00 = 4 \text{ hours}$.
Ann took $\boxed{4 \text{ hours}}$ to complete the race.

2.4.7)

The race started at 08:00 in London.
The information about South Africa time being two hours ahead is extra and not needed to answer the question about the time in London.
The time in London when the race started was $\boxed{08:00}$.