"I take the job on with a high level of trepidation, slight levels of fear, but absolute delight in becoming your CEO," he said.
He thanked his predecessor for "bringing the business back from the brink" and the bank had a "special obligation" to British taxpayers because of the bailout.
Thanks to the bailout the UK Government is a 73 per cent shareholder.
"We have a higher standard that we have to live by than any other bank in the UK," he said.
"We can find that daunting, or we can find that aspirational."
Last year the bank reported a £2 billion loss, its eight annual loss in a row, and Mr McEwan received £3.8 million - double the amount he made in 2014.
Before the Royal Bank of Scotland he was at the Commonwealth Bank in Australia, which he said turned itself from being the worst customer-service business to the best in the Australian marketplace.
Putting customers first has been a constant mantra in his latest role.
"One of the reasons I got this job is I was able to demonstrate to the board that I know what a great business that looks after customers looks like and what it does," he said.
He told Hawke's Bay Today he is not daunted by the ongoing challenge.
"Changing business for the better excites me," he said.
"Most obstacles are just a new challenge to be overcome."
He left Hastings Boys' High School in the mid-1970s for Massey University in Palmerston North but returned in the early 1980s to work for Unilever's food branch before moving to Wellington in the mid 1980s.
He was personnel manager at Dunlop New Zealand until 1986 when he joined National Mutual New Zealand for 10 years before becoming AXA New Zealand CEO.
He then went to First NZ Capital Securities and then held various roles at Commonwealth Bank of Australia before joining the Royal Bank of Scotland.
He met his wife playing basketball at university and they have two daughters.
"My wife and I still have very good friends in Hawke's Bay and we visit annually when we are back in New Zealand.
"Hawke's Bay has a special attraction for us, given it is home, but also a wonderful place to bring friends to visit the vineyards, the scenic attractions and the great weather. We also own a section at Aramoana Beach where we camped for 14 years when the family were younger."
He said he has moved six times in his career "and each move adds something to your experience in life".
"From a work perspective, you learn a lot that you can use in your next role."
It has also been good for his family, he said.
"Our family has always approached location changes as an adventure where you meet new people, experience different cultures and visit new and exciting places.
"You have opportunities to meet new people and build new friendships. You experience different cities and cultures.
"As a family we have always seen these moves as adventures and we have all grown because of them. The move to the UK has added to this experience work-wise and has opened up the opportunity to visit European countries as well as travelling extensively in the UK and Republic of Ireland."
His family life has also enriched his work life - he was recently quoted as saying his daughter's poor experience dealing with banks while starting a business was a reminder of the necessity of a good customer experience.
While his Scottish name did no harm when he took the reins at the Scottish bank neither did his nationality, he said.
"New Zealanders tend to be quite direct, in a nice way, and can generally get on with most people.
"We are also used to working across a broad range of operations in a business as New Zealand businesses are smaller and you understand broadly how the parts connect to make up the whole.
"This helps when you are asked to run bigger businesses, as you understand what makes them work."
An affable manner and HR background also held him in good stead. "Having good people skills also helps connect a very diverse group of people you find in a UK bank."
He was in the news again this week - the bank paid Her Majesty's Treasury £1.2 billion as a step towards returning the bank to the private sector.
The payment puts an end to an agreement with the Government, preventing bank dividends to any shareholder before the Treasury, but will harm its efforts to achieve a profit in the first quarter of this year.
A dark cloud hangs over potential profits in the form of a potential multi-billion-pound penalty from US authorities, for the way the bank packaged sub-prime mortgages into bonds in the run-up to the Global Financial crisis.
It is not alone. Ratings agency Moody's warned litigation and conduct costs from past mistakes were a "downside" risk for the other four major UK banks.
Mr McEwan said every job had its challenges, the bigger the better. "Some people enjoy jobs with big challenges and I am one of those people. "
When asked how New Zealand was placed for growth in world markets he said it was well-respected globally but must not rest on its laurels.
"The country sits on the top of the ease-of-doing-business-with scale and its clean/green standing is still attractive for many countries.
"New Zealanders are used to travel and realise they need to be proactive in developing markets globally and we work well with a wide variety of cultures.
It must keep focusing on new markets "to continue to grow and create prosperity for all New Zealanders".
