The intended target of the IRA terrorist attack was prime minister Margaret Thatcher and her Tory Cabinet, who were staying there during the Conservative Party conference.
The flag flew at half mast over the hotel as staff and members of the public gathered in the lobby for a minute’s silence to remember the injured and the dead.
The brief ceremony took place in front of a plaque marking the bomb’s 25th anniversary, which was unveiled by former Tory minister Lord Tebbit.
The Grand’s general manager, Andrew Mosely, said: “The 60 staff who are on duty today gathered around the plaque that was unveiled by Lord Tebbit.
“I said a few words to pause and reflect and remember the five people who were killed and 34 injured, the guests at the hotel, members of the community, the emergency services and so many other people who were affected by what happened that night.
“Then we stood for the minute’s silence, which was conducted solemnly and correctly. Hotel guests joined us as well as members of the public, one of whom had bought a bunch of flowers to lay at the base of the plaque.
“It was the right thing to do, the bomb blast happened here and we should remember it and the reasons why it happened.
“The message we want to send above all else is that we have not forgotten what happened here 30 years ago.’’
Patrick Magee, who planted the deadly device, will return to the city tonight to take part in a panel discussion following a screening of documentary Beyond Right & Wrong at The Old Market in Hove.
The programme follows the story of Jo Berry, whose father Sir Anthony Berry was killed in the explosion, and her reconciliatory journey with Magee.
Magee was handed eight life sentences at the Old Bailey in 1986, with a recommendation he serve a minimum of 35 years.
He was released in 1999 under the Good Friday Agreement - having served 13 years for the crime.
Ms Berry believes it is important Magee attends tonight’s documentary screening.
She said: ‘’For me, inviting Pat to be there (today) is to show a living example of reconciliation and the power of empathy. It is really important to have him there to demonstrate that.
‘’Yes, some people will be upset but I think that for peace sometimes you have to take these risks.’’
Magee, who has declined to speak to the press ahead of tonight’s event, has changed considerably, according to Ms Berry.
She added: ‘’When he planted the bomb he wasn’t seeing human beings. It was a strategy and now he sees human beings and wonderful human beings. It has been about him getting his humanity back. That has changed him, definitely.
‘’He regards me as a friend. He knows that my dad was a wonderful human being and he knows that some of the qualities I have came from my father and that weighs heavily on him.’’
Lord Tebbit, writing in the Sunday Telegraph, said he could not forgive the bomber.
The then trade and industry secretary was severely injured in the blast and his wife Margaret was left paralysed from the neck down and needing 24-hour care.
He wrote: “I am often asked if I can find it in my heart to forgive the creature, Patrick Magee, who planted the bomb,” he wrote.
“That, of course, is not possible, for Magee has never repented. It was not he who decided to commit that crime in Brighton, financed it and procured the bomb that he planted. If he was repentant and wanted to see justice done, he would have told the truth and named those guilty of those crimes.”
He added: “Yet, for many victims of the conflict, including my wife, justice has not been done. Think of ‘the disappeared’ who are denied even the dignity of a decent burial by the silence of those who know the truth. And without that justice, peace in the province is not as secure as it might be.”