Ostensibly, Mr Portillo will be in the colony as part of routine inspection of troop duties. However, he will barely have time to shake hands with the troops up near the Chinese border before being whisked off to see the remnants of the naval presence and the newly arrived Black Watch battalion who have barely had time to unpack.
The suspicion about political motives has been heightened by Mr Portillo's insistence that his press entourage for the trip should consist of political correspondents rather than defence writers who would normally be present on occasions such as these.
He had been scheduled for a three-day stay in the colony but the lack of a Conservative majority in the House of Commons meant he needed to be present for a parliamentary vote yesterday and will not be able leave London until this afternoon.
From Hong Kong, he will fly to Brunei, where Britain has 950 troops including 600 Gurkhas, all paid for by the Sultan.
The visit is also expected to result in the signature of a deal to buy up to three corvettes - fast but heavily armed small warships of about 1,500 tons each, designed for policing the country's Exclusive Economic Zone and protecting natural resources as well as possible use against the growing threat of piracy.
The deal for the ships, their equipment and related training could be worth up to pounds 250m. Although relatively small in defence terms, the timing of the deal is highly significant in the run-up to the general election and also to a major defence exhibition, called Idex, in Abu Dhabi next month.
The United Arab Emirates could be in the market for a much bigger order - six patrol boats and six corvettes.
Ministry of Defence sources said Mr Portillo was due to meet the Sultan during the visit on Thursday. Also on the agenda is a joint military exercise to take place in April called Setia Kawan II, involving 2,500 British personnel, and the Defence Procurement Memorandum of Understanding signed by the Sultan and John Major in 1994.
The brevity of Mr Portillo's visit to Hong Kong serves to underline a feeling of British neglect in the colony. Both Malcolm Rifkind, the Foreign Secretary, and John Prescott, Labour's deputy leader, have truncated recent visits because of parliamentary pressures at home.
Mr Rifkind's visit last week has stirred some controversy because of suggestions that he used his very short time in the colony to engage in Conservative Party fundraising.
However, this has been categorically denied by Wilma Croxen, the vice- chairman of the Conservatives Abroad organisation in Hong Kong who organised a cocktail reception for Mr Rifkind at Hong Kong's luxury Mandarin Hotel.
"It was a fund-losing event," she said regretfully, not enough money was raised from the pounds 24 entrance fee to cover the hire of the room and the drinks. Mr Rifkind stayed for less than half an hour and the subject of party funds was not raised.
It is a far cry from the days when Hong Kong tycoons were among the Conservative Party's main benefactors and John Major was able to walk away from a select dinner with the colony's tycoons after pledges of millions of pounds had been made.
Those same tycoons now want nothing to do with anything British; their benevolence is strictly reserved for the incoming Chinese regime.