The former senior Army bomb disposal officer with the Royal Logistic Corps was shocked to be told the news of his resignation was to appear in The Sun, a jury was told yesterday. Colonel Robert Seddon was warned by another officer that his decision to resign his post was to appear on the front page of the tabloid who had not contacted him before the piece was published.

Seddon also told the court that he had been "upset" when he had seen the article which, he believed, implied he had resigned "in a fit of pique". Instead, he said, he had left the army for a mixture of personal and professional reasons. "I wanted to do something else" he added.

The testimony came on the ninth day of the trial of four former senior Sun journalists, and an army officer and his wife over charges relating to alleged payments to civil servants and others for confidential information. One MOD official, the court has already heard, was paid £100,000 by News International for material she supplied for army stories.

Cross-examined by defence barrister Geoffrey Cox, Colonel Seddon agreed he had appeared on a Panorama documentary the evening that the piece was published, but said that he had not mentioned his pending resignation to anyone at the BBC. The front page article he said, implied he was leaving due to disenchantment that the training of bomb disposal personnel had been stopped, leading to a rise in casualties in Afghanistan. The Colonel said that had been an issue in 2009, but by the time of his resignation the army was on the right track although he was "a little bruised" about the process.

Seddon also said that the article contained information about his personal relationship with his men which "were certainly not in the public domain", and that he found much of the language in the story "sensationalist".

Earlier the jury heard from Barry Burton the former Private Secretary to Defence Secretary Dr Liam Fox. The witness was questioned about a Sun article that revealed that while he was Defence Secretary, Fox had aides accompany him in holiday to Spain. This story was described in court as the first of a series that led to Fox resigning as a minister. Burton was also asked if he thought the leak to The Sun was a "deliberate political attempt to undermine Fox's credibility?”. The civil servant said he had no direct knowledge of that.

In the dock at the Old Bailey are The Sun's former chief reporter John Kay, executive editor Fergus Shanahan, deputy editor Geoffrey Webster and Royal editor Duncan Larcombe. Charges relating to alleged misconduct in a public office are also being heard against former army officer John Hardy and his wife Claire.

All of the defendants deny all of the charges. The trial continues.