Debbage and Evans were visiting London from Norwich for a Countryside Alliance East Anglian rural Oscar rural enterprises champion award reception for their farm shop and garden centre business and were walking just metres from the place at Westminster where the incident took place.
Masood ran over pedestrians in his car and stabbed a policeman before he was shot dead.
Debbage spoke of his shock as they heard gunshots ring out while walking outside of the Palace of Westminster and told to run by nearby police officers.
They had been at the awards event at the House of Lords and as they were leaving they "heard shots just a few yards ahead".
Debbage said: "A policeman turned to us and yelled at the top of his voice, 'run, run away'. There were people in front of us who turned and fled. There was another policeman on one of the turnstiles into Westminster who told us to come in as it was safe.
"Before we knew it we were standing in the cloakroom of the House of Lords.
"We were locked in and we could hear lots of shouting outside.
"If we had not taken a selfie as we emerged from Parliament we would have been about at the place where he crashed his car into the railings."
He says since returning to the garden centre a car alarm in the car park "tripped something" within him and brought back the harrowing memories.
Debbage says he has had to concentrate on business since returning to Green Pastures managing the Mother's Day weekend in the centre's restaurant and plantaria.