His firm is Mr Greer's oldest client and has been one of the most lucrative accounts for the controversial lobbyist.
Mr Greer organised Parliamentary lunches on DHL's behalf and introduced the company to senior politicians. This was part of a drive by Mr Allen to raise DHL's profile in an increasingly competitive industry. Mr Greer also ensured the company was up to speed on any legislative changes. The sale of Parcelforce from the Post Office was a big lobbying issue, with DHL keen to ensure it did not go to a rival.
One of its wheezes was to take a stand at the party conferences and within minutes of a key speaker sitting down, make their text available to delegates. This year at the Labour conference, while controversy about Mr Greer raged around Blackpool, his client had its usual place in the exhibition hall.
Mr Allen remains firmly in the background, eschewing all personal publicity. Well-known in high Tory circles, he is thought to be a strong supporter, although DHL was at pains to stress yesterday that the firm is politically neutral.
His firm said it "enjoys excellent relations with all three main political parties and it does not make any donations to any fighting funds. DHL (UK) is an apolitical company and works to build understanding of our business within the political framework existing within the UK".