They said their final goodbye and parted at Euston, where he took the westbound Circle Line train and died in the Edgware Road blast.
Mr Downey, whose family hailed from Ireland, was a human resources systems development officer for the Royal Borough of Kensington and Chelsea.
He was survived by his wife, his father, his twin brother Liam, his sisters Mary and Julie and another brother, Shay.
Mr Downey, who was born on 15 March 1971, grew up in Corby, Northamptonshire and met Veronica when they were both teenagers.
They studied business and finance together at Tresham College in Kettering, Northants and married in 1999.
He worked in the payroll department at Corby Borough Council before moving to a similar job at Kensington and Chelsea Council in 2001.
Councillor Merrick Cockell, the leader of the council, said: "He was a very friendly and approachable person and very knowledgeable and skilled at his work.
"Everyone who knew Jon and who worked with him, will miss him enormously."
The Downeys moved to Milton Keynes in 2003 to be closer to London.
Mr Downey was a big fan of Liverpool Football Club and a keen walker.
His widow said: "He was a big joker who enjoyed winding up his friends. He lived life to the full and enjoyed the day for the day.
"Jon was also very cerebral. He was very conscious of those less fortunate that himself. At his funeral, friends were invited to donate money to the NSPCC."
She said: "Jon was a good listener and a good friend to people in need. He was a rock to me when I was going through a difficult time at work."
Mr Downey and his wife were members of the Woodlands Trust and a group of 50 relatives and friends gathered in woodlands near his home and planted trees and shrubs in his memory.
There is a bench at the site with his name on it and another one outside Kensington and Chelsea Town Hall.
His wife said they had planned to move to Ireland before his life was cut short.
Mrs Downey said: "Ironically Jon used to pick up a packet of cigarettes and announce 'These will never kill me'. He was right."
On the morning of 7 July, Jonathan Downey, 34, left his home in Milton Keynes, Buckinghamshire, with his wife Veronica for their daily commute to London.