1. Now Mary could have no illusions that she was anything except a prisoner.

That在这里是连词，连接结果状语从句，意思是“以至于......”。

e.g. Double over the map that we can read it more easily.

把地图对折起来，这样看起来更容易。

e.g. I will give you all the facts that you can judge for yourself.

我会给你所有的事实以便你可以自己判断。

2. She was shuttled from house to house under the watchful eye of the Earl of Shrewsbury, who got the unenviable job of being her jailer.

from house to house：从一个屋子到另一个屋子，挨家挨户

e.g. They went from house to house, begging the people for bread.

他们挨家挨户地向人们乞食。

e.g. The police at once began a search from house to house for a criminal.

警方立刻开始按家搜索罪犯。

under the watchful eye of：在(某人)的警觉目光下；在…的监视下

e.g. There were demonstrations in the streets today, under the watchful eye of police.

今天，在警方的监视下大街上进行了游行。

e.g. Children swim at the pool, under the watchful eye of lifeguards.

孩子们在救生员的监护下在水池里游泳。

3. Mary Stuart had to be kept a long way away from any possibility of rescue, far away from Scotland, far away from London, far away from the coast.

kept sb a long way away from something：使某人距离......很远

e.g. John is kept a long way away from drug.

约翰被支开得很远，让他远离毒品。

far away from somewhere：距离某地很远

e.g. Far away from home, the overseas student dream of returning to his own fireside.

这位远离家乡的海外学生渴望着回家。

e.g. And he spent his senility on an archipelago, far away from here.

当他年老的时候他住在了一个群岛上, 远离这里。

5. But wherever she was, Mary Stuart become maximum security problem number one, not just a headache but a magnet for conspiracy.

not... but..: 不是......而是......

e.g. What I want is not money but love.

我所需要的不是钱而是爱情。

number one：最好，自身利益

e.g. I can certainly assure you I'm looking after number one all right.

我可以肯定地向你保证,我会照顾好自己的。

e.g. George is number one around here and I am his number two.

乔治是这里的头号人物，而我是他的副手。

e.g. Air and water pollution are our Number One priorities.

空气和水污染是我们关注的首要问题。