Freya and Graham McAnally had booked to have their nuptials at Manchester Town Hall in the north of England, and were stunned to find The Iron Lady crew shooting scenes in the building, which has similar architecture to the Houses of Parliament in London.
And the pair couldn't believe their eyes when they stepped out of the registry office to find Streep in her Thatcher finery smiling and applauding.
Freya says, "It was all very surreal - Meryl Streep was standing there dressed as Margaret Thatcher. It almost feels like it didn't happen.
"I thought it was amazing, the last thing you expect is an A-List celebrity at your wedding."
And the generous actress made sure the pair's nuptials got off to a great start by gifting them with signed photos, champagne, flowers, a glass vase and a copy of the film's call sheet for the day.
Graham adds, "They went above and beyond what they had to - it was lovely."
The Schindler's List star was left devastated when Richardson passed away in 2009 after suffering a brain injury in a skiing accident in Montreal, Canada.
Neeson sparked rumours he had started a new romance when he was spotted holding hands with British businesswoman Freya St Johnston last month (Sep10).
But new reports have emerged suggesting he has begun dating Leslie Slater, who he met on a flight to Paris, France six weeks ago.
The pair was spotted sharing an intimate meal at a New York restaurant, before Slater spent several hours at Neeson's apartment.
An onlooker tells Britain's The Sun, "When his date arrived they gave each other a big hug and kiss. Then for the next couple of hours they barely touched their food as they laughed and stared into each other's eyes."
Another source tells the publication, "Leslie's been going on about Liam for weeks and he texts her all the time. They get on really well and, due to her work, she travels extensively and can get about easily. She agreed to see him in New York and they went out together a few times. Liam seems to really like her."
The Schindler's List star was left devastated when Richardson passed away in March 2009 after suffering a brain injury in a skiing accident in Montreal, Canada.
But now Neeson has reportedly gone public with a new romance with British businesswoman Freya St Johnston.
The actor left Nobu restaurant in London on Friday (03Sep10) clasping the 35 year old's hand, reports Britain's The Mail On Sunday.
But Johnston has refused to confirm or deny the relationship, telling the publication, "I am not saying anything whatsoever."