Nabil Shurafa breaks off his explanation of the trials of being a travel agent in a territory where the large majority of citizens cannot travel, to take a call from one of his few lucky clients. It is a bank employee booked on a Cairo-Damascus Egyptair flight at 2.30am tomorrow. "You'll get the bus from Rafah at 11. Be sure to tell the [Egyptian] soldier that you have to be at the airport by 1am at the latest. The flight goes from terminal three."

Mr Shurafa is happy to be having this conversation at all. For it was only after the lethal raid by Israeli commandos on a Turkish-led flotilla at the end of May that Egypt decided to open the Rafah crossing each day so as to escape the stigma of its involvement in the sealing of Gaza's borders.

Numbers admitted through the crossing are heavily restricted – out of a population of 1.5 million, it is 150 at most a day who leave, and around 20 of those are Mr Shurafa's clients. From the crossing to Cairo airport, they can expect to pay £11 – for the compulsory bus ride, overseen by the Egyptian security services.

Given the heavy restrictions – with eligibility mainly confined to medical cases, students with visas to study abroad, those with foreign passports and some businessmen – the numbers crossing and the number of Mr Shurafa's clients are unlikely to grow unless Egypt relaxes the regime further or Israel starts to let travellers out through the Erez crossing.

Nobody, including Mr Shurafa, has any idea how long the opening of the Egyptian border will last. And even if it is sustained, he reckons it will take him two years to recover the big losses he incurred over the past three years, let alone start to break even on the $5,000 (£3,200) a month it costs him to run his office. But at least for now, he has some regular – if modest – business. For a change.

There is probably no better way of examining the see-sawing impact of the last turbulent half-century on Gazans' freedom of movement than through the prism of Mr Shurafa's family business.

Sticker after sticker on the shopfront of its pleasantly cool office in eastern Gaza City testifies to the airlines it has represented since Shurafa Travel and Tourist Company was founded by his father, Hashem, in 1952. The large relief map of the world and four striking mirrors painted by a local artist with images of the Eiffel Tower, Big Ben, the Leaning Tower of Pisa and the Statue of Liberty are reminders of its two busiest eras: from 1952 to the Six Day War in 1967, and the tantalisingly hopeful post-Oslo years, from 1993 up until the Second Intifada of 2000. In the – relatively – halcyon days when Shurafa Senior started the business, the better-off minority who could afford to travel from then-Egyptian-controlled Gaza were able to drive their cars straight to Cairo airport.

Oil production in the Gulf was expanding and the demand for well-trained Palestinian teachers as well as technicians was on the increase. It wasn't long before the agency became one of only two IATA-accredited outlets in Gaza, and the only General Sales Agent in the Strip for the old British Overseas Airways Corporation.

"In those days, if a Palestinian bought a ticket directly at Cairo airport, the airline still sent the commission to us," said Mr Shurafa wistfully. "They protected their agents. They don't do that now."

But during the Israeli occupation of Gaza from 1967 to 1973, business virtually dried up. His father nevertheless kept it going, on a care-and-maintenance basis – a decision which the son clearly regards as a model for his own desperately lean period over the past three years. Then, travel became possible again, as Gazans were able to leave, this time through the Erez crossing via Israel. It was in the 1990s, however, that business really took off again.

In the wake of Oslo and the return of Yasser Arafat to Gaza, the company was awarded a "Top Ten" certificate by British Airways for "outstanding sales achievement" in 1996/7. Construction boomed, the company became the official agent to the Palestinian Authority and Mr Shurafa remembers employees of the Antrim-based Mivan company, who were building the European Hospital at Khan Yunis, constantly using his services to travel to and from the United Kingdom.

Travel seemed set for a golden era when Gaza International Airport was opened by Mr Arafat in 1999 and Mr Shurafa was on the inaugural two-hour Fokker 50 flight to Istanbul. "I remember being asked by an American reporter what I felt before the flight left and I said: 'To you this may seem like a small airport but to me it seems bigger than JFK.'"

It was not to last. The destruction by Israeli incursion and bombardment was finished off by Palestinian scavenging. Now the airport is little more than a pile of rubble.

Yet the business – at an albeit severely reduced level – survived throughout continued warfare and the drying up of custom from thousands of diaspora families who used to make annual trips to the territory and who now fear they would not be able to return to their homes and jobs.

It was only after Hamas's enforced seizure of full control of the Strip in June 2007 and the subsequent total closure of the borders, that the Shurafa family business was threatened with going under. But somehow Mr Shurafa kept going – under nightmarishly loss-making conditions.

Given that the only opportunities for travel were the (at best) quarterly two- or three-day openings of Rafah, when thousands of would-be travellers would swarm to the crossing, there was never any certainty that his few clients would get through. Because of airline restrictions on flight changes, Mr Shurafa would take the money and frequently issue the ticket at the last minute, as the client arrived at the airport.

"Sometimes we failed; if there were no seats left I would just make a 20-50 shekel (£3.30-£8.40) charge and give him the rest of the money back. But I couldn't shut down [for the night] because I had to speak to my customers at any time." Often, because of frequent electricity cuts, he has had to use a generator to power up his laptop to check availability and issue a ticket.

One of a handful of would-be passengers waiting for service at the company yesterday, a 25-year clothier Hamdi Ayed, told his own story about the changes inflicted on Gaza's economy over the last three years.

Whereas Mr Ayed used to buy from the hundreds of Gaza clothing factories, they are now shut down because of a lack of raw materials, So he is armed with a visa to set out for China next weekend to buy cheaper clothes for import through Ashdod port and the Kerem Shalom crossing.

It's not certain that he would revert to Gaza suppliers even if the new easing of the embargo brings some local manufacturers back to life. But he is certainly rewarding Mr Shurafa with the customer loyalty he has earned over the years. Why was he using the agent? "We know these people," Mr Ayed explained.

Mr Shurafa argues that his costs – especially in relation to negligible revenue – have been markedly higher over the past three years than for travel agents elsewhere – thanks to the high cost of goods smuggled in through the tunnels and the high charges imposed by a Palestinian telephone monopoly.

What he would most like to see is Israel allowing in the cement needed for the large-scale construction that would in turn help to revive his own business to the glory of the old days. "If I only thought about economics I would have closed down a long time ago," he remarked.

But he clearly sees his continued operation of the business as an example of summoud – Palestinian steadfastness. "This is my country and this is a family business and this has helped us to resist the siege."