Rather, the profiles of those involved in the course of the campaigns, which have lasted in various phases since 1972 until the present day, show that they fall into a variety of categories.
Some are known and highly experienced republican activists, despatched from the north or south of Ireland; some are only teenagers, with little or no republican traces; some have lived in England for most of their lives.
What is perhaps extraordinary is the fact that so many people - almost certainly hundreds of them - have run the risk of becoming involved in terrorist activities, knowing that if caught they can expect lengthy jail sentences in unfriendly conditions in British prisons.
Yet the flow of IRA members has been kept up for more than two decades, the organisation's methods and techniques becoming far more refined than they were in the 1970s when a gang of republicans bombed the Old Bailey in central London and then, ludicrously, attempted to board the next plane back to Belfast.
Some of those involved have been hardened IRA members, often from families with republican links stretching back beyond the present troubles. At least two of those involved in the early days had brothers killed by the British Army in Belfast.
The "Balcombe Street gang" of the early Seventies - so-called because they were arrested after a siege at Balcombe Street in central London - serve as an example of a group who were apparently intent on fighting on until they were captured or killed.
Another example of what might reasonably be called a desperado was Paul Magee, an IRA man who killed a special constable in Yorkshire during a routine vehicle check in 1992. Magee appears to have considered that he had nothing left to lose, since he was on the run from police in both Northern Ireland and the Republic.
As he had escaped from prison in Belfast after being jailed for the murder of an SAS man, he knew he already faced a life sentence if apprehended.
In at least two cases in recent years the security services were clearly on to the terrorists right from the start, following them from the moment they arrived in Britain.
They could have been spotted at ports or airports, or they could have been reported missing from their usual haunts by police in Belfast or Dublin.
In other cases, teenagers have been sent over to the mainland, obviously in the hope that their lack of open republican links mean they will escape the attention of the security forces.
Some involved have had criminal rather than terrorist records. One man jailed had been to prison almost a dozen times for non-republican offences which included fraud and theft, while another had a record of sex offences. More than one jailed in England has been said to have a drink problem.
In yet another pattern, first or second generation Irish people in Britain have become involved. These are probably of particular value to the IRA, since they tend to have English accents and have an intimate knowledge of how to avoid drawing attention to themselves.
There have also been cases of the IRA recruiting people resident in England who have both an Irish background and far-left political beliefs.
Some of those who have come before the courts have been described as minor characters. When a Belfast republican, Patrick Magee, was given eight life sentences for his part in the 1984 Brighton hotel bombing, in which five people were killed, another man who pleaded guilty to involvement in the attack was given only a four-year sentence. Described as shaking as he stood in the dock, he was said to be a reluctant recruit to the IRA, having been a patient in a psychiatric hospital where he was treated for manic depression. A doctor described him as "a quiet, charming gentle and very troubled young man who often tended to be morose and withdrawn". Magee is still in jail.
This is, however, very much an exception to the rule that those involved in the bombing campaigns have generally shown fervour and dedication to their cause.
But the range of different types involved helps illustrate why it has proved so difficult for the security services to combat the IRA's efforts to take its war to England.
The Englishman -
Ryan was killed in November 1991, together with Patricia Black, an IRA member, when their bomb exploded prematurely outside a theatre in St Albans, where an Army band had been playing. Born in Harlow, Essex, of Irish parents, Ryan lived in England until he was 19. In 1985, he moved to a republican area of west Belfast with his mother and almost immediately became involved in republican work, helping to sell Sinn Fein newspapers.
Those who knew him in Belfast described him as bright, intelligent and dedicated to republicanism.
His English accent marked him out as being of potential use to the IRA in Britain, and he was sent there as part of an active service unit, probably less than a year before his death.
Speaking at Ryan's funeral, a Sinn Fein leader said: "Frankie and Patricia are not alone. They are representatives of a generation of Ireland's youth who have acquired the skills to remain hidden, who come forward when required to do so. How will the British defeat this invisible force?"
The lecturer -
Feilim O hAdhmaill
O hAdhmaill was arrested early in 1994, just six weeks after arriving in England to take up a post in Preston as a lecturer on social policy. In November 1994, he was jailed, aged 36, for 25 years for conspiracy to cause explosions.
He had republican form, having faced a charge of murdering an RUC constable in the early 1980s. The case was dropped. He was a close friend of Bobby Sands, the near-legendary IRA hunger-striker.
Born in Birmingham of Northern Irish parents, O hAdhmaill had moved back to Belfast at the age of four. There he gained a doctorate with a thesis on "the dynamics of the ghetto", lecturing in Belfast before applying for the job in Lancashire.
Caught red-handed with a car containing explosives, he admitted IRA membership but mounted the defence that he intended only to store them because the IRA was involved in a peace process.
In a speech from the dock, O hAdhmaill said he hoped the process "leads to a permanent end to the war in my country and the establishment of a lasting and just settlement".
After a lengthy campaign, he was transferred to serve his sentence in a Northern Ireland prison in July 1995.
The student -
Kevin Barry O'Donnell
O'Donnell was 19 when he was arrested in London in 1990 by police who found two Kalashnikov rifles in the boot of a car in which he was travelling.
A native of County Tyrone, he was at the time of his arrest taking a poultry husbandry course at an agricultural college in Shropshire. A year later, there was surprise when a jury acquitted him of terrorist charges. There was speculation that the verdict might have been influenced by the freeing of the Birmingham Six the day before.
O'Donnell told the jury: "I do not support the IRA. I don't agree with killing and bombing. I come from a devout Catholic family. There's no way I support the taking of life." Following the trial, O'Donnell was re-arrested and deported to Northern Ireland.
In Tyrone a month later, he was charged with possessing a rocket-launcher, but not jailed. The following year, he was part of an IRA unit which attacked an RUC station in Coalisland. Immediately after, he and three others were shot dead in an SAS ambush. He was given an IRA funeral.
The southerner -
Kelly, who was described as a typical country boy from a rural community, was jailed for 25 years in 1993, at the age of 41. Southern Irishmen rarely surface in an active IRA role in Northern Ireland, but over the course of the troubles many have played an active role in terrorist operations in Britain.
Kelly, from Co Laois, was arrested in the act of driving a lorry containing a large bomb into the centre of London. He was also convicted of attempted murder on the grounds that an associate had fired shots at a pursuing policeman.
Leaving school at the age of 13, Kelly worked as a general dealer, lorry driver and crane driver, living for much of his life in England.
He had a chequered criminal career, with convictions for kidnapping a horse-dealer in the Republic and for importuning and indecency.
At the time of his trial, it was said that Kelly was "in a small way of business", frequently travelling between England and Ireland where he traded in goods including computers, kettles and umbrellas. Some time ago, he was diagnosed as suffering from skin cancer. Following a lengthy campaign, he was transferred first to Northern Ireland and then to a prison in the Republic.