Page 626 - Practical English Usage 3ed - Michael Swan, Oxford

Present perfect and past perfect tenses can emphasise the idea of completion.
You're not going home until you've finished that report. I waited until the rain had stopped.
5 structure with Not until . ..
In a literary style it is possible to begin a sentence with Not until . .. , using inverted word order in the main clause (see 302).
Not until that evening was she able to recover her self-control.
Not until I left home did I begin to understand how strange my family was.
6 until and by: states and actions
We use until to talk about a situation or state that will continue up to a certain moment. We use by (see 117) to say that an action or event will happen at or before a future moment. Compare:
- Can I stay until the weekend?
Yes, but you'll have to leave by Monday midday at the latest. (= at twelve on Monday or before.)
- Can you repair my watch ifI leave it until Saturday?
No, but we can do it by next Tuesday. (NOT ••• ttntil next Thestldy.)
7 until and before
Not until/till can mean the same as not before. I won't be seeing Judy until/before Tuesday.
And both until and before can be used to say how far away a future event is. It'll be ages until/before we meet again.
There's only six weeks left until/before Christmas.
603 up and down
1 'towards/away from the centre'
up and down are not only used to refer to higher and lower positions. They can also refer to more or less important or central places. (Trains to London used to be called 'up trains', and trains from London 'down trains'.)
The ambassador walked slowly up the room towards the Queen's throne. She ran down the passage, out of the front door and down the garden. We'll be going down to the country for the weekend.
But in the US downtown refers to the central business/entertainment area.
2 north and south
People often use up and down for movements towards the north and south (perhaps because north is at the top of a map page).
I work in London, but I have to travel up to Glasgow every few weeks.
3 'along'
Sometimes both up and down are used to mean 'along', 'further on', with little or no difference of meaning.
The nearest post office is about halfa mile up/down the road.
up and down 603
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