Mr Flanagan grew up in Napier, where he attended Napier Boys' High School.
He lived in London with his wife and young son and worked as the head of foreign exchange institutional sales for National Australia Bank.
He had also worked for HSBC and the Royal Bank of Scotland.
His friend Tony Brown, a financial trader based in Singapore, said he was "shocked" to receive a phone call saying Mr Flanagan had been found dead.
"He was such a jovial, jolly, happy chappy. He was always there for a laugh, always up for a beer, and he had a truly wicked sense of humour. He just fit in with anybody."
Napier Boys' High School archivist and historian Phillip Rankin said Mr Flanagan was a prefect of the school in 1986. He was also leader of the brass band, in which he played the cornet alongside EIT's newly-appointed deputy chief executive Mark Oldershaw.
Mr Oldershaw and Mr Flanagan bonded over music, winning a national duet championship during their school days.
Mr Flanagan would later be best man at his wedding.
He described Mr Flanagan's death as "a truly tragic accident".
"Undoubtedly it's come as a shock to everyone. It's all a bit surreal."
Although he had lived in London for about 10 years, Mr Flanagan remained proud of his Hawke's Bay and Napier roots.
"He was full of life. He always gave things a go and certainly lived life to the max."