The Prince of Wales and Duchess of Cornwall have arrived in a smog bound New Delhi amid revelations of Charles' financial affairs back home.
Charles is due to hold talks with India's prime minister Narendra Modi but the meeting is likely to be overshadowed by reports, by the BBC and the Guardian, that the heir to the throne invested in an offshore carbon credit trading company, then lobbied for two climate change deals to be altered.
The royal couple began the last leg of their autumn tour by flying from Malaysia to India and landed at an airforce base in the Indian capital where the sun was obscured by a smoky haze.
Smog had descended on the city on Tuesday, causing some to panic, according to reports, when they woke up and found the capital engulfed.
The Indian Medical Association has declared a public health emergency, urging administrators to "curb this menace" and all Delhi schools have been closed until Sunday.
The serious problem with the pollution comes after emissions from diesel engines and coal-fired power plants were further exacerbated by smoke from farmers burning crop stubble and from fireworks set off for last month's Diwali celebrations.
India is the last leg of an 11-day trip, which has seen the prince and duchess tour Singapore, Malaysia and Brunei.
Although the stop to India is brief, just two days, the meeting with the leader of the world's largest democracy is an important one.
Charles has spoken of his passion for the Commonwealth during the tour, and with a major gathering of leaders from the family of nations being staged in London next April, the meeting of the prime minister and the prince will further strengthen UK-India relations ahead of the summit.
According to reports, the leaked Paradise Papers show Charles' private Duchy of Cornwall estate paid 113,500 dollars (£58,000) in 2007 for 50 shares in the Bermuda-registered Sustainable Forestry Management Ltd in 2007.
Following the purchase, Charles lobbied for a change to two climate change deals that would have directly benefited the business, the BBC and the Guardian said.
A spokesman for Clarence House denied that Charles had spoken out on the two deals in order to benefit financially.
"The prince has never chosen to speak out on a topic simply because of a company that The Duchy may have invested in," he said.
"In the case of climate change his views are well-known, indeed he has been warning of the threat of global warming to our environment for over 30 years."
The spokesman added that carbon markets were just one of many strategies Charles had championed to try and slow the pace of climate change.
Margaret Hodge MP, a former chair of the Common's Public Accounts Committee, told the Guardian: "What is clear is that there should be proper transparency of all investments made by the Duchy of Cornwall, that the Prince of Wales should not be involved in investment decisions and that the Treasury should monitor the investments to ensure that the reputation and integrity of our royal family is protected."