Kate Middleton shows off baby bump at reception for her art charity (VIDEO)

She took advantage of a warm summer night as she arrived at the National Portrait Gallery in a duck egg blue cocktail dress and no coat

Pregnant Duchess of Cambridge was full of the joys of Spring tonight as she showed off her blooming baby bump in a sleeveless dress.

Kate, who is almost seven months pregnant, made her second public appearance in as many days visiting the National Portrait Gallery for her charity The Art Room.

She was the guest of honour at a reception to celebrate the charity's 11th anniversary for 250 guests including children and their teachers.

The Duchess made a speech in which she sounded less stilted than usual

Looking tanned in a pale blue Emilia Wickstead cocktail dress and grey suede heels with her hair half-up and wavy, Kate arrived at 7.30pm and was greeted by Art Room founder Juli Beattie.

She watched a brief video about the charity before making her second speech in as many days.

Portrait of Kate Middleton by Paul Emsley which was unveiled today at the Gallery in London

Kate said she had been "overwhelmed" by the "transformational" work of the Art Room, adding: "I'm a firm believer in the power of art to make a difference."

Afterwards fellow Art Room supporter broadcaster Jon Snow said to laughs from the Duchess: "If she can turn out at this stage of her pregnancy for this cause it must be big!"

The Art Room helps school children aged five to 16 boost their self-esteem through art and the Duchess became their patron last January.

She chatted to some children who have benefited from their classes.

Tiertha, 15, from Regent's School in Camden said: "I have a picture of Kate on my bedroom wall in her wedding dress.

Kate smiled and waved as she was driven home

"I told her and she said 'wow' and she asked if William was in it as well and I said 'yes' and she said 'good'."

Andrew, 13, said: "She asked how the Art Room has affected me and I said it makes me feel calm for the weekend. I go for two hours on a Friday."

Six months along: The Duchess' bump was more evident than ever as she met staff at The Art Room

Kate is also patron of the National Portrait Gallery, where her first official portrait hangs as well as several portraits of members of the Royal Family.

Award-winning artist Paul Emsley created the large head and shoulders painting of the Duchess set against his trademark dark background.

The crowds and photographers were still out in force at the end of the evening

Despite mixed reaction, Kate was delighted with the painting, saying: "It's just amazing, I thought it was brilliant."

Art Room Founder Juli Beattie, said: "The Duchess's continued commitment and endorsement of our work has been an invaluable asset in securing the foundation and laying the path for future growth of The Art Room."

Tonight the charity announced it has launched a new room in Ealing thanks to generous donations from the ICAP charity day and has an ongoing appeal to launch one in Edinburgh.

Kate, who is due to give birth in mid-July, plans to continue royal duties throughout her pregnancy until mid-June, and her schedule has been organised so she has several public engagements in a row then the chance to rest behind the scenes.

This week she is busy with a visit to a primary school on the Shameless estate in Manchester yesterday and a trip with William and Harry to the Warner Bros studios in Hertfordshire on Friday.