Another surprise public appearance by the Queen - this time at Paddington Station.

She's attended the opening of the Elizabeth Line, a new train line on the London Underground that opens to the public next week.

UK correspondent Gavin Grey told Kate Hawkesby the project is well over budget and well behind schedule.

He says it was due to open in 2010 with a budget of NZD$30 billion, which has now risen to NZD$40 billion.

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