The attacker, who managed to get close to Mr Roy in the crowd and threw black ink on him, claimed to be Manoj Sharma, a lawyer from Gwalior, Madhya Pradesh. He has been detained.
The Sahara chief was driven down from Lucknow to Delhi last night in a Mercedes escorted by police cars. (Who is Subrata Roy? 10-point cheat-sheet)
Mr Roy, 65, was arrested on Friday after failing to appear at a Supreme Court hearing - which he says he missed to attend to his ailing mother - related to a multi-billion-dollar Sahara investment scheme that was later ruled to be illegal. (Sahara chief Subrata Roy arrested, son says as law abiding citizen he surrendered)
Sahara has vast real estate holdings and interests in media companies and hotels, including the Plaza Hotel in New York and London's Grosvenor House. The company says it has a net worth of $11 billion or Rs 68,200 crores.
The Securities and Exchange Board of India (SEBI) says Sahara failed to comply with a 2012 court order to repay thousands of crores to investors. Sahara says it repaid most investors and that its remaining liability was less than the 5,120 crore rupees it deposited with SEBI. (Can't handle this level of agony and humiliation: Subrata Roy in statement before arrest)
"The question is money. Where is the money and when will it be paid," said Dushyant Dave, a Supreme Court lawyer who has represented Sahara in the past.
The Supreme Court had ordered Sahara to disclose the details and source of funds from which it said it repaid investors, but a lawyer for the regulator told the court in late January that Sahara had not given the details. (What may have led to Sahara chief Subrata Roy's arrest)
Sahara had offered to give SEBI title deeds of properties it said were worth 20,000 crores as security, but the regulator said the properties were far over-valued. The court also ordered that Sahara not sell any of its property.
Sahara's core business includes selling financial products, largely to small investors in towns and rural areas. It was two such products, later ruled illegal, that drew SEBI's attention.