1. There were many political heavyweights for whom Mary was a legitimate, attractive alternative to Elizabeth.

【解析】for whom Mary was a legitimate, attractive alternative to Elizabeth是限定性定語從句修飾后表示人且在定語從句中做介詞for的賓語的先行詞heavyweights。

2. They were not just a bunch of wild-eyed Catholic dreamers, but men close to the heart of Elizabeth's government.

【解析】這句話用not...but...來連接并列的表語成分，一個是：a bunch of wild-eyed Catholic dreamers（一群狂熱的天主教追隨者），另外一個是：men close to the heart of Elizabeth's government（伊麗莎白政權的核心人物）。

在第二表語中，close to the heart of Elizabeth's government是帶有介詞的形容詞短語作后置定語，修飾名詞men。

3. Their most ambitious plan was to annul the Bothwell marriage and marry the Queen of Scots to the premier duke of the realm, Thomas Howard, Duke of Norfolk.

【解析】這個句子是用并列連詞and連接了2個并列分句，一個是：Their most ambitious plan was to annul the Bothwell marriage（他們的野心勃勃的打算廢除和博思韋爾的婚約），另一個是：marry the Queen of Scots to the premier duke of the realm, Thomas Howard, Duke of Norfolk.（讓蘇格蘭女王嫁給王國第一公爵諾福克公爵，名字叫做托馬斯·霍華德）。

在第一個分句中，謂語是be+動詞不定時表示將來發生的事情。

在第二個分句中，Thomas Howard是做duke 的同位語，補充說明duke的名字。Duke of Norfolk是做Thomas Howard的同位語。

4. Although Norfolk may have been a Catholic at heart, he was, like so many of this time, outwardly at least, a conforming Protestant.

【解析】這是含有讓步狀語從句的復合句。主句是：he was, like so many of this time, outwardly at least, a conforming Protestant，讓步狀語從句是：Although Norfolk may have been a Catholic at heart。

在主句中like so many of this time（就像這個時代這么多人一樣）是作方式狀語，outwardly at least（外表上看來至少）是做程度狀語，a conforming protestant（順服的天主教徒）是做表語。

5. There was, though, a different kind of fury waiting to happen.

【解析】waiting to happen是現在分詞作主語fury的補足語。