He continued to travel to New Zealand to spend time at the family farm at Matauri Bay in Northland.
Priest in Charge at the Holy Trinity Cathedral Bruce Keeley said they were expecting in excess of 1000 people to attend the memorial service. The cathedral's maximum capacity is about 1200.
"We're certainly expecting a large crowd, probably around 1000. But you can't RSVP so we can't be sure," he said.
If there weren't enough seats, the main cathedral doors would be opened so people could gather on the forecourt.
"I do known that there are some pretty, beautiful, elaborate floral decorations that are being arranged. I think they are going to be made to match to some degree the floral arrangements from the service in Britain."
The service, which starts at 2pm on Wednesday will be followed by a reception at the Northern Club on Princes St.
The memorial will be officiated by Reverend Warner Wilder, who was formerly chaplain at King's College where Sir Douglas went to school.
He said the service would reflect as much as possible the funeral service that was held in London.
Sir Douglas was awarded a CBE in 1991 for his services to business management and was knighted in 2010.
He was ranked 10th on the 2016 NBR Rich list with a total worth of $930 million.
Sir Douglas' father, Sir Kenneth Myers, and grandfather, Sir Arthur Myers, were both successful brewing magnates.
Besides accomplishments in the brewing industry, Sir Douglas put $3m into Auckland University's Kenneth Myers Arts Centre, created the Sir Douglas Myers Scholarship worth $100,000 a year to study at Cambridge University, and supported Auckland University's business school.
He is survived by wife, Barbara, and children Jessica, Laura and Campbell.
