Frank and Pat couldn't hide their true feelings, and later started an affair - leading to one of the soap's most memorable scenes when Frank showed up on Pat's doorstep, naked except for a spinning bow tie and a grin.
In the early 1990s, Frank and Pat were married - until he fled Walford after inadvertently causing the death of a homeless man killed in a fire at his car lot, started by Phil so Frank could claim on the insurance.
Pic: BBC] Ross Kemp is returning as Grant Mitchell, we'll see Walford legend Natalie Cassidy's final scenes as Sonia, and the identity of Cindy's Christmas Day attacker will be revealed.
One of EastEnders' most famous love triangles, the tangled love lives of Pat, Peggy and Frank carried storylines for several years.
You can't talk about EastEnders' biggest moments without mentioning Christmas 1986, when 30 million people tuned in to see the womanising Dirty Den serving wife Angie with divorce papers, after discovering she had been faking a terminal illness.
