Karti Chidambaram wanted an upgrade to business class when the Central Bureau of Investigation was taking him to Delhi from Chennai for questioning, sources told INDIA TODAY TV on Wednesday. The CBI was firm that rules only permit travel by economy class, they added.

"Karti then tried to persuade Jet Airways to let him use his frequent flyer mileage to get an upgrade. The CBI resisted and managed to get him to fly economy," said a senior agency official.

While Karti returned from London early morning, his father - former finance minister P Chidambaram - is also expected to return from London where he cancelled a lecture at Oxford University.

Even as the CBI got a day's remand to question Karti further, a damaging statement given by incarcerated businesswoman Indrani Mukerjea to the Enforcement Directorate was leaked.

The statement was recorded recently by ED under Section 50 of Prevention of Money Laundering Act which is admissible in court of law.

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Mukerjea, who is being tried for the murder of her daughter, told the ED that she and her husband, Peter Mukerjea, "met Sh P Chidambaram in his office in North Block where Sh P Chidambaram told them to help the business of his son, Karti, and to make foreign remittances for this purpose".

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They also claimed to have met Karti in Hotel Hyatt in Delhi where a demand for illegal gratification of $1 million was allegedly made.

It was said that Karti Chidambaram allegedly suggested the names of Chess Management and Advantage Strategic (ASCPL) as alternatives to make payments.

Indrani Mukerjea, the ED document says, has also made a similar statement before the CBI under Section 164 of the Criminal Procedure Code (CrPC) where she confirmed the payments of $7,00,000 abroad.

Karti's lawyer Kapil Sibal said, "If there was an iota of evidence that there were payments made to foreign accounts abroad, it would have been admitted to by the CBI and ED when they were opposing in the Supreme Court Karti's plea to travel abroad.Had there been payments made abroad in bank branches and where Karti could have tampered with the evidence, would the court have allowed him to travel."

The ED says, correspondingly, four invoices of $7,00,000 drawn by ASCPL, its Singapore subsidiary, another associate company (Northstar Software Solutions Pvt Ltd) and Geben Trading limited were seized from the hard disks of his chartered accountant, Bhaskararaman. ED sources say with this statement they hope to get to P Chidambaram.

If the CBI wished to question him, they should have sent a summons - Abhishek Manu Singhvi

"His arrest is imminent," an officer told INDIA TODAY TV. Abhishek Manu Singhvi who appeared for Karti at the Patiala House Courts said the CBI's contention that Karti was not cooperating did not have merit because Karti appeared every time a summons was issued.

Singhvi said if the CBI wished to question him, they should have sent a summons.

Besides, unlike others like a Nirav Modi, or a Vijay Mallya, or arms dealer Sanjay Bhandari, Karti Chidambaram was not running away, he said. "He left with the court's permission and returned each time."

On Wednesday, Karti's initial questioning began at 8 am in the Chennai International Airport and continued for some time, with formalities for his arrest being simultaneously processed inside the airport.

None of Karti's supporters had a chance to meet him. At about 10.45 am, Karti was taken to Delhi by the CBI officers to be presented at Patiala House court. At Karti's Nungambakkam residence, a large crowd of Congress supporters started to gather.

Within an hour of Karti being whisked away to Delhi by the CBI, his mother Nalini Chidambaram, a well known lawyer herself, left for Delhi. When INDIA TODAY TV tried to speak to her at her residence and later at the airport, she refused to comment.

-With inputs from Akshaya Nath in Chennai