The recent tragic suicide in Villawood Detention Centre serves as a reminder of the causal link between self-harm and incarceration. Mandatory detention for unauthorised boat arrivals was introduced by Paul Keating's Labor government in 1992. There were cases of self-harm in Australian detention centres some two decades ago and they continue today.

The first boat arrivals reached Australian shores in 1976 - from Indochina. Since then there have been boat arrivals every year except 1980 and the period from 1982 to 1988. Some 2059 boat people arrived in Australia during the period of Malcolm Fraser's government but the large number of Indochinese refugees who entered Australia did so by air on valid visas following offshore processing. This fact is generally not known today.

When the Keating government introduced mandatory detention, there had been fewer than 500 unauthorised boat arrivals in the previous three years. John Howard substantially toughened the laws covering asylum seekers in 2001, a year in which there were 5516 boat arrivals. Julia Gillard raised the issue of offshore processing again this year - in which about 5000 boat people reached Australia by the end of September. Viewed in this light, Keating's decision seems harsh - another unknown fact.

Among asylum seeker advocacy groups, Fraser is widely praised and Keating all but ignored. Yet the figures reveal that it was during the prime ministerships of Howard, Kevin Rudd and Julia Gillard that unlawful boat arrivals were high. Agree with the details of his policies or not, Howard effectively stopped the boats. Gillard has a problem today partly due to the fact that in 2008 Rudd and his immigration minister, Chris Evans, softened the policy that Labor had inherited from the Coalition.

It is likely that asylum seekers will always be with us. This is broadly accepted within the country. Each year Australia welcomes about 13,500 migrants under the refugee and humanitarian intake.

There is a myth that Australians are tough on asylum seekers who arrive by boat but soft on those who come by air. On the ABC1 program Q&A on September 20, the Chaser's Craig Reucassel said asylum seekers who land in Australia on aircraft "don't get put into detention centres". He added: "If you come by boat you're some kind of criminal; if you can afford Qantas, it's fine."

This is hopelessly wrong. Anyone who arrives in Australia without a valid visa, and/or who seeks asylum on arrival, is placed in detention. It's just that it's very difficult to get on a plane in a foreign country destined for Australia without a valid visa. Those who manage to do so have considerable ingenuity. The unauthorised arrivals who reach Australia in large numbers come by boat. It does not take much ingenuity to get on a boat in an Asian port, having paid money to people smugglers. But it does require enormous courage, since death by drowning is a possible outcome.

The combination of ingenuity and courage means that most unauthorised arrivals who reach our shores and obtain permanent visas make good citizens. They tend to obtain jobs and there is no evidence that those groups find their way to any significant extent into crime, still less terrorist activities.

My wife has been involved in helping asylum seekers for many years, albeit not on a soapbox. In late 2004, shortly after the Coalition's defeat of Labor at the election, I approached Howard to talk about the insights I had gained in the handling of unlawful arrivals by boat and by air. The meeting is referred to in Margot O'Neill's book Blind Conscience (New South, 2008).

I understood the problem any government would face if it had to deal with the level of unauthorised boat arrivals that had been prevalent in 2001 (and which are confronting Gillard today). My advice was that the Coalition should display a "red flag" out the front but show a "green flag" out the back. In other words, it would make sense to do as much as possible to stop the boats but to deal promptly and sympathetically with those who make it to our shores.

Howard received many representations and much advice around this time. Whatever his rationale, the fact is that when the Coalition lost office in 2007 it had a reputation for being tough on asylum seekers - yet the detention centres were all but empty and unlawful arrivals had slowed to a trickle. The essential error of the Rudd government was to replace Howard's red flag with one of amber colour.

The recent unanimous decision of the High Court in the matter of two anonymous Sri Lankan asylum seekers is unexceptionable. What the judges said, including several who were appointed by the Coalition, is that asylum seekers who end up on Christmas Island should receive procedural fairness. If governments are intent on thwarting unauthorised arrivals they need to stop boats landing on the mainland or on Christmas Island. Once they arrive, it's too late for red flags.

Gerard Henderson is executive director of The Sydney Institute.