Heavy noun phrases

A noun phrase (NP) is particularly likely to have its own IP if it is heavy (= long, consisting of several words). Since the grammatical subject of a sentence is often just an NP, there is often an intonation break between the subject and the rest of the clause or sentence:

The head of a large 'school | has a lot of responsi'bility.
The people I've been 'talking to | were quite 'definite about it.
London and the south'east | will have 'showers. || The 'rest of the country | will be 'dry.
The speaker has considerable discretion about this. A separate IP for the subject of a clause is more frequently found in reading aloud and in formal speeches to an audience than in everyday conversation (Cruttenden , 1997:70).

The grammatical subject is particularly likely to have its own IP if it is different from the subject of the preceding sentence or clause, i.e. if there is a change of subject:

I thought the food was excellent. || And salmon ⤵⤴quiche | is something I adore
Making the subject NP into a separate IP has the advantage of allowing the speaker to place contrastive focus on it by locating the nucleus there. Even every light (= short) NPs can be made into separate IP to allow this:

The ⤵⤴children | say they don't like her. || But \/I | think she's wonderful.
Cats and ⤵⤴dogs | can make wonderful companions.
Objects, too, are followed by an intonation break if they are heavy:

I gave the 'book you asked about | to the girl at the 'checkout.