Ph.D. were a British duo best known for their UK top 10 hit "I Won't Let You Down" in April 1982, which had been a hit the previous year throughout Europe.

"I Won't Let You Down" is a song by British band Ph.D., released as the second single from their eponymous debut studio album (1981). It entered the Australian charts in October 1981 and reached number five; it entered the UK Singles Chart in April 1982 at number 34, peaked at number three the following month. It went on to become the 23rd best-selling single of 1982 in the UK.