Pippa Middleton and boyfriend Nico Jackson are apparently back in London after their trip to India.

The sister of Catherine Duchess of Cambridge was spotted at London's Heathrow airport last Sunday with boyfriend Nico Jackson pushing their luggage cart. They both look red-faced in the photographs, proof that they enjoyed the sunshine in South Asia.

Middleton was wearing a white cardigan over a floral-print shirt from Cashmere by Tania, gray jeans and brown boots. On the other hand, Jackson sported a navy knit sweater over a checkered shirt, dark jeans and a pair of beat-up Converse sneakers.

A friend of the couple confided to The Daily Mail about their pact to each other to travel to lots of exotic destinations before walking down the aisle to start a family.

'There will be lots of trips like this in coming months,' says the source.

Last September, rumors have been circulating that Jackson had proposed to Middleton. but they are keeping their engagement under wraps. This is so as not to take the attention away from her sister Kate, her brother-in-law Prince William and her then newborn nephew George.

There are also claims that the stockbroker has asked his family and friends to prepare for a spring wedding, and that he plans to make the official announcement this month.

'Nico can't stop talking about it,' says another source, adding, 'It's been the source of much excitement among his friends. He and Pippa want everything to be just perfect.'

However, there no signs of engagement could be seen just yet, not even at their recent appearance during the Sugarplum ball last month.

Middleton and Jackson were first seen together in February during a holiday in Mustique with her parents and the Duke and Duchess of Cambridge. Since then, there have been numerous instances where the couple have been seen together but they are yet to be invited for the royal Christmas dinner at the palace.