In the 10 years between the two attacks, Britain has beefed up anti-terror legislation and stepped up its emergency preparedness, but the number of fighters travelling to join jihadists has multiplied.
The four suicide bombers of July 7, 2005, who killed 52 people, said they were inspired by Al-Qaeda, while the Tunisian gun massacre of June 26 in which 38 tourists died was claimed by the Islamic State group.
The country will observe a minute's silence at 1030 GMT after having made the same gesture on Friday in honour of its latest victims of terror.
The July 7 ringleader Mohammed Sidique Khan, a father-of-one whose parents were immigrants from Pakistan, was angry at British foreign policy in Iraq and said he wanted to avenge the deaths of fellow Muslims.
John Tulloch, a British-Australian man who was on the train targeted by Khan, remembers the moments after the blast: "The darkness, smoke, glass everywhere."
There were "horrifically wounded people right next to me, the dead young man spreadeagled at my feet," he told AFP.
The physical pain endures from the shrapnel lodged in his head but more painful still are the images that still form "a frightening tapestry of memory".
