Protests to Bucharest made immediately after Ceausescu's toppling in 1989 fell on deaf ears. Now the Foreign Office has stepped up the pressure, formally requesting the Romanian government to return the insignia - which includes an intricate collar adorned with golden roses and sapphires - or at least explain where it is.
Sergiu Celac, Romania's ambassador in London, says he finds the row 'extremely embarrassing' and promises the matter is being pursued 'with all due diligence' back home. Diplomatic sources in Bucharest, however, are convinced that the splendid regalia was undoubtedly stolen in the chaos of the Romanian revolution and that now, according to one, it is 'probably in the hands of some fat cat party member who parades around in it giving private showings for friends'.
The Grand Cross of the Order of the Bath was awarded to Ceausescu during a state visit to Britain in 1978 on the recommendation of the then prime minister, James Callaghan, and his foreign minister, David Owen. Even then it was steeped in controversy. According to Lord Bethell, MEP for London North- West, it should never have been awarded in the first place. And it should certainly have been withdrawn long before December 1989, the month in which Ceausescu was toppled and executed.
'Ceausescu's human rights violations were clear even in the 1970s,' said Lord Bethell. 'But the award simply served to reinforce his credibility back home.'
Indeed, alongside the French Legion d'Honneur, presented by General Charles de Gaulle personally, the Order of the Bath insignia was prominently displayed in a Bucharest museum.
Soon after taking the Order of the Bath away, the Queen returned to Romanian authorities the Star of the Socialist Republic of Romania First Class, an award with which she had been presented during the London visit of the Communist dictator.
All recipients of the Order of the Bath pledge to return the insignia - or at least the collar, estimated to be worth some pounds 15,000 - when they die, thereby enabling it to be 're-cycled'.