我们正要出发，这时下起雨来了。

相关链接

sb was/were doing ... when ...某人正在干......这时......

sb had just done ... when ...某人刚刚干了......这时......

I had just lain down when the telephone rang.

我刚刚躺下，这时电话铃响了。

4、He is lost in London.

他在伦敦迷路了。

"迷路"的三种表达方法

他们在森林里迷路了。

①They were lost in the forest.

②They lost themselves in the forest.

③They lost their way in the forest.

5、Permit me to lead the way, sir.

先生，请让我来带路吧。

注意

permit sb to do sth=permit doing sth

allow sb to do sth=allow doing sth

advise sb to do sth=advise doing sth

forbid（禁止）sb to do sth=forbid doing sth

①We don't allow anybody to smoke in our room.

　　=We don't allow smoking in our room.

我们不允许任何人在我们房间抽烟。

②He advised us to do more reading in our spare time.

　　=He advised doing more reading in our spare time.

他建议我们业余时间多读书。

6、As a matter of fact, I landed in Britain by accident.

事实上，我在英国上岸是偶然的。

as a matter of fact=in fact=in effect=in practice事实上

by accident=by chance=accidentally偶然地