Is "you know" in the middle of the sentence necessary?
No. Using "you know" is definitely not necessary for this sentence to be complete. Using "you know" in this type of sentence is just a way to fill space in the sentence. It gives the speaker time to collect his or her thoughts and figure out what she wants to say next. Victoria Beckham is thinking of what her son said to her, so she uses the words "you know." It is very common in English and you will hear them used in weird places that do not really make sense. Another example sentence would be: "You know, Annie, your plane is going to leave soon." Remember; this meaning isn't always the same for every sentence with the words "you know", but in this video, the above explanation is correct.
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