Last week saw the completion of one of the most gruelling round-the-world expeditions ever undertaken.

Over four years after setting off from Tower Bridge, Sarah Outen again kayaked under the London landmark, thus coming full circle and completing the trip.

Sarah cycled, kayaked and rowed 25,000 miles. Along the way she was saved from the middle of the Pacific after being hit by a tropical storm and then from the Atlantic as a hurricane closed in. She cycled in temperatures ranging from 40 degrees in the Gobi Desert to -40 degrees during the North American winter. The 30-year-old came close to death when she was sucked under the bows of a container ship in her rowing boat.

Legendary explorer Sir Ranulph Fiennes said upon the completion of her journey: “I am very impressed by Sarah’s incredible fortitude and endurance against great odds. This has been a seriously tough expedition but she has done it. My thoughts and admiration are with her as she now completes her brilliant and highly successful London2London journey.”

Between all that, Sarah managed to write regular updates from her journey for The Independent, keeping readers informed of her progress and what is truly entailed when such an ambitious task is undertaken.

It started in April 2011 when she kayaked from London to France. From there she took to her bike and cycled a punishing 11,000 miles across Europe, Russia and Asia before kayaking to Japan.

In 2012 she made her first attempt to row solo across the Pacific but this was cut short three weeks in when she was hit by a tropical storm and had to be rescued.

Writing about the experience in her blog for The Independent, Sarah told: "Water had started to leak into my cabin via the hatches and before long a ribbon of water was streaming in through my main hatch, like a tap left open. Given the extraordinary force of the waves I wasn’t surprised and I gritted my teeth each time a wave smashed directly into the bulkhead, waiting to see what would happen."

Ultimately, Sarah was rescued by the Japan Coast Guard, but she was unperturbed.

Sarah with a message for the middle of the Pacific for The Independent's readers

A year later she returned to try again and with it became the first person to row from Japan to Alaska, although looking back, it was a leg that coincided with her most terrifying moment of the trip. "Going under the bows of the container ship in the North Pacific in 2013 was a moment I thought would be my last," she remembers. This was her blog after 100 days at sea.

Explaining how she dealt with the lengthy periods alone on the ocean, Sarah explains how she got through it: "Just knowing that you have to keep going to get home is always a good motivation. You cannot just hop on a bus if you get tired. I break big tasks into small goals and celebrate tiny gains. It is all about finding your own way through, whatever it takes. I work with a lot of schools through sports charity Inspire + and so I always found phone calls home to schools very motivating."

Dealing with the homesickness was also tough: "I really missed my fiancee Lucy (whom I met in 2013) and so we talked as often as we could on the phone," Sarah told The Independent. "I was lucky enough to have her join me on the winter cycling leg in North America last winter."

However, one of the most challenging aspects of the trip was something unexpected: "I have been surprised by just how challenging it has been to switch from one mode of transport to another with limited transition times e.g. from bike to boat in a day after six months of the former in 2011 and more recently from rowing to cycling to kayaking within days of each other."

After arriving in Alaska, Sarah kayaked one of the toughest routes in the world with kayaking partner, Justine Curgenven - the 1500 miles through the Aleutian Islands. They are believed to be the first people to do this. It was here that Sarah recalls her stand-out moment from the trip. "Looking up from my hair washing in an Alaskan stream to find a brown bear marching upstream to see me. I was naked. He was curious. It was pretty intense."

She then cycled across North America through one of the toughest winters on record to Cape Cod.

From here she set off to row solo across the Atlantic to the UK but after 143 days at sea and having rowed 3600 miles, Sarah was forced to call for a pick up due to Hurricane Joaquin closing in.

Then last month, she began the final leg of the journey, cycling and kayaking from Falmouth back up to Tower Bridge.

After all of that, would one of The Independent's 50 most influential women in sport recommend anyone else undertaking such a trip?

"The thing I would recommend is chasing your dreams, being unafraid to try something difficult or new and embrace change and failure."