Crossing the border between India and Pakistan at Wagah, Sadiq Khan walked into Pakistani territory with the traditional border guards welcoming him with a salute, and an entourage awaiting him.
The visit of Khan is a part of his "London is Open" campaign, media reports said. He had earlier stayed in India for three days where he met politicians and other important personages in Mumbai, Delhi and Amritsar.
BBC has defended their reporter's bold question by pointing out that it originated from the fact that many, including Punjab's chief minister Shehbaz Sharif, had called the mayor's trip "homecoming".
The Mayor was received by Lahore Mayor Colonel (retd) Mubashir and Lahore Commissioner at the border.
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During the meeting, both the leaders held discussion on trade and investment opportunities in Pakistan.
Mr Khan said that the cities of London and Lahore enjoyed good relations and expressed the desire to enhance cooperation and investment with Lahore in various sectors.
The prime minister said that successful counter-terrorism efforts have made Pakistan an opportune destination for United Kingdom businesses.
Speaking at a dinner reception given by the mayor of Lahore, Mr Khan said he was impressed by the hospitality of the people of Lahore.
The mayor was born and raised in Tooting, South London.