Watch: ITV's Phil and Holly pay respects at Queen's Lying in State
Thousands of members of the public have been queuing to view the coffin.
And video footage shows the duo, who were both dressed in black, looking serious as they walked through the area.
According to the Daily Mail, Schofield and Willoughby - who was wearing a black facemask - were there filming a segment for their ITV show.
This Morning was not on air on Friday (16 September) amid the ongoing coverage of the Queen's death and in the run-up to the funeral next week, but it will be back on Tuesday.
Willoughby, 41, and Schofield, 60, are not the only ITV stars to have been seen at the Palace of Westminster.
She kept her fans updated about it on Twitter, saying that being able to be there and pay her respects was "worth every minute" of the queue.
Reid also shared tips for members of the public who were planning to go and wait in line.
Her advice included wearing the "comfiest" shoes and taking along toilet paper.
She also advised people to carry wet wipes for hands instead of sanitiser, as it would be confiscated by security as they went in.
The Queen’s lying in state at the Palace of Westminster is open 24 hours a day until it closes at 6.30am on 19 September, the day of the late monarch's funeral.
Yahoo has contacted ITV for comment.