Beginning with Series 4, it becomes clear that the weight of always having to be "the wise one" takes a heavier toll on her than many would guess, and she is increasingly shown leaning on Shelagh (formerly Sister Bernadette) for counsel and support; nevertheless, her faith is not shaken and she remains a serene, guiding presence for all of Nonnatus House.
One of the UK's earliest registered nurses, and the last surviving founder of Nonnatus House, Sister Monica Joan (whose birth name was Antonia Keville) retired from practice prior to the events of the series.
It is evident that Sister Monica Joan is well-educated and well-read, as she frequently quotes a wide range of authors from Greek philosophers and Freud, to Keats and Shakespeare.
In the final episode of Series 1, after recovering from pneumonia, she is arrested for stealing trinkets from the market: some ribbons, a handkerchief, a china robin and several other things.
But their engagement breaks down when Trixie discovers that Tom has a placement in a slum in Newcastle, an industrial city in North East England.
She returns to Poplar and continues to work with in the community, she is involved in several cases around abortion and is present when Valerie is called to her grandmother's pub.
Matthew eventually turns out to be the owner of many properties in Poplar and offers to become a beneficiary to Nonnatus House in memory of his late wife, allowing their services to continue.
One scene shows Sister Bernadette looking in on the midwives' room while they are drinking and gossiping, but then the door closes; it is a life that cannot be open to her while she remains a nun.
As of the 2012 Christmas Special and from Series 2 onward, it becomes clear that Sister Bernadette has fallen in love with the local physician, Dr Turner.
After recovering from a short bout with tuberculosis, Sister Bernadette leaves the convent and reverts to her birth name of Shelagh (née Mannion).
After a year of maternity leave, Shelagh returns to Nonnatus House as senior midwife and nursing sister to cover for Barbara, who is taken ill and eventually dies.
A neat and forthright woman, Phyllis is viewed at first as somewhat snobby; she is vegetarian and is not scared to put her ideas forward to improve Nonnatus House.
Before becoming the handyman at Nonnatus, he was in the British Army, during which time his wife was killed, leaving his daughters to be shuffled around between several of his family members, causing him great pain and tempting him to desert.
Nurse Anderson is religious, joining a local Black house church after finding a larger, White-majority congregation unwelcoming of her "kind".
She sometimes expresses prudishness, such as when Nurse Dyer asked for her assistance with a sex education class, but she ultimately shows tolerance for the changing times and environment.
Middle class, loquacious and good-humoured, Sister Hilda is a great facilitator in the social setting with her gregarious nature, readily putting people at ease.
An experienced midwife, she attended a girl's Catholic boarding school, and worked and lived in the East End during the Blitz in the WAAFS, but has not been back for 20 years and is surprised at the multicultural and geographical changes to the area.
She has a distinctive bright 1960s dress sense, is funny and enthusiastic, bringing a breath of fresh air to Nonnatus, but is often a worry to Sister Julienne as she frequently fails to conform.
Furthermore, the deprivation of the East End is a huge culture shock for the young woman who has enjoyed a privileged upbringing in the home counties and spent time in Paris before training as a nurse.
Halfway through Series 3, Alec dies in a tragic accident and after his funeral, Jenny travels to the Nonnatans' mother house in Chichester for compassionate leave.
She returns to Nonnatus House after taking time to grieve, and decides to begin working at the London Hospital in the Maternity Ward.
She eventually decides to pursue a career change to care for those with terminal illnesses; she leaves Nonnatus House to work at the Marie Curie Hospital in Hampstead.
It is shown in the Series 3 Christmas Special that she eventually married Phillip and started a family, and still kept in contact with the friends she made at Nonnatus House.
In the 2014 Christmas Special, Cynthia decides to become a postulant and leaves Nonnatus House for six months of training, promising Trixie and Patsy that she will return.
Like Chummy before her, Patsy works with Fred as a leader of the local Wolf Cub Scouts; she recruits Delia to help teach first aid.
They plan to move into a flat together at the end of Series 4, but their future is shattered when Delia is involved in a cycling accident and suffers a serious head injury which results in amnesia, leaving her with no memory of Patsy.
Following her father's death, Patsy seems to drop all correspondence with Delia, appearing as though she would not return to Nonnatus House, but she comes back to London on the day of Tom and Barbara's wedding.
By the following Christmas, she has regained her memories of Patsy and their relationship, and at the start of Series 5, despite continued efforts from her mother to take her home to Wales, Delia accepts Sister Julienne's invitation to board at Nonnatus House when she returns to work at the London in the coming months.
In Series 7, Barbara dies after contracting meningococcal sepsis, leaving Tom, Nonnatus House and the rest of the Poplar community heartbroken and shattered.
They eventually start dating after a long period in which Jenny continues to mourn her loss of Jimmy, but who encourages her to enjoy life and Alec.