Alec Jesmond was the boyfriend of Jennifer Lee in Series Three of Call The Midwife. He was portrayed by Leo Starr.
Alec is a friend and colleague of Jenny's lifelong friend/former love interest Jimmy. Jimmy, after getting married to a woman he had gotten pregnant, wanted Jenny to find happiness with someone else since they were no longer in a position to potentially find it together. He introduced Alec to Jenny and helped Alec secure a dance with her on a visit to a bar, which bloomed into a relationship between the pair.
Alec, like Jimmy, is an architect who works for the city. Alec provides Jenny, and therefore her fellow nurses, with the information that Nonnatus House is scheduled to be demolished.
Alec professes his love to Jenny on Chummy's birthday as the pair walk home from the pub. Jenny is uncomfortable and acts as if he said nothing, simply thanking him for a wonderful day. He later comes to see her and apologizes for making her uncomfortable, explaining that he did not mean to and instead telling her that he likes her very much. She tells him she likes him very much as well.
In Episode Four of Series Three, Alec falls through unstable scaffolding, shattering his femur. Later, his foot must be amputated in order to save his leg. Unfortunately, due to the fracture of his leg, an embolism formed---a clot, formed because of the fracture that came loose and traveled to his lung--and he passes away while Jenny is helping Sister Winifred deliver a baby. Jenny is devastated and takes leave from Nonnatus House to grieve at the Motherhouse. Alec's mother was unable to attend his funeral as she lived abroad in Ceylon (known today as Sri Lanka), but the mothers of Poplar had joined the local choir and sang at the service with one mother telling Shelagh "We're all mums now. We're doing this for her".
Later, when Jenny returns to Poplar, she meets an elderly lady who has finally been able to leave her house after her daughter has given birth. The lady says something about grief and Jenny begins to bawl, saying that she doesn't know how to move on when the pain is so fresh, but the lady replies "You just keep living until you are alive again." Jenny takes the advice to heart, and soon enough, lives again after Alec's death.