NEW DELHI: “Humein bhi kabhi mehman-nawazi ka mauka dijiye (Let us also be your host),” Nawaz Sharif told Narendra Modi when the Indian PM called his Pakistani counterpart from Kabul on Friday to greet him on his birthday.The call, at 11:30 am India time, triggered a flurry of activities on the Christmas day that ended with Modi’s impromptu trip to Pakistan hours later that many describe as a diplomatic masterstroke. Modi always had a desire to combine a trip to Kabul and Islamabad, said government officials. But the fact that Sharif was in Lahore , and his invitation to the Indian PM to visit his Raiwind home, raised security concerns among Indian officials.ET spoke to senior government officials aware of the deliberations between both the PMs. The officials said the pit-stop was confirmed over two calls between both sides after India stood assured of foolproof security in Lahore. When Sharif invited Modi to Pakistan, the Indian PM is said to have replied that he did have a wish to come to Islamabad, “par aap to Lahore mein hain (but you are in Lahore)”. Sharif told Modi that he was in Lahore for the marriage of his granddaughter and couldn’t return to Islamabad on the same day. “Aap Lahore mein ghar aa jayiye, Lahore ke darwaze bhi aap ke liye khule hain (Come to my Lahore home, the doors of Lahore are also open for you),” the official quoted Sharif as telling the Indian PM. Modi discussed the possibility of a Lahore stopover with NSA Ajit Doval and the SPG officials, who had concerns over the security paraphernalia.“Islamabad has an institutionalised security protocol and setup for VVIP visits from the US and elsewhere which we were comfortable with even in the case of a sudden trip. But the Lahore surprise pit-stop was a big challenge for the SPG,” a senior official told ET. Sources said there were some concerns — one, can an IAF plane in which Modi was travelling back from Kabul be allowed to land in Lahore given the sensitivities that the IAF had bombed that area during the 1965 war. And two, will Modi have to take the 45-kilometer road journey from the airport to Sharif’s Raiwind Palace through the heart of Lahore.Pak got back to the Indian side promising foolproof security at the Lahore airport and assured a Pak Air Force Chopper would fly both PMs to Raiwind and back, officials said. During the conversation with Modi, Sharif had told him he would receive the Indian PM at the airport.“Sharif flying in the same chopper with Modi was the biggest assurance that security would be top-notch,” a senior official said. Both PMs had another phone conversation subsequently in which Modi confirmed to Sharif that he would land in Lahore later that evening and visit his Raiwind house. Indian High Commissioner to Pak, TCA Raghawan, travelled straight to Raiwind, four hours from Islamabad, as he had no time to reach the airport to receive Modi.