You need to declare it and they would doubtless peruse the Gazette newspaper to see if you might have gone BR before. The good news is that because it was more than 10 years ago your new bankruptcy should not be affected by the previous one. For example, if you had gone bankrupt within 10 years of the previous time you would face an automatic 5 years before discharge. As it is more than 10 years you would be autmatically discharged in 1 year provided your discharge is not suspended (which would be unusual in all cases). You must declare it, however, as it would likely be held against you by the OR if you didn't. Unless you didn't and convinced the OR you had a big case of amnesia (!).