Leah Croucher's mum writes her daughter a heartbreaking letter on her 21st birthday today in Milton Keynes

And, in a bid to spread the appeal to find Leah as far and wide as possible, the Citizen helped the family get the letter in The Sun newspaper, which has a circulation of more than 32 million readers worldwide.

The letter, as printed in The Sun's centre pages today, is below:

Dear Leah,

Today is your 21st birthday. It should have been a day of excitement, a day I was hoping to keep the promise I made to you four years ago at your brother Haydon’s surprise 21st party.

That day I crossed my fingers and hid them behind my back as I smiled and said, “I promise I will not throw you a surprise birthday party on your 21st. We will go on holiday instead.”

Leah, I had no intention of ever keeping that promise.

Yes, we wanted to take you on holiday, we wanted to take you to Costa Rica for your 21st.

But I was planning one big surprise party before we went, with family and friends all there to help celebrate.

We had a meal with family for your 18th — that is what you wanted. You were never one to look for attention.

Always trying to hide in the corner, usually attached to you phone.

You like a family party, you just don’t want to be the reason it is being held.

Tomorrow it is another milestone in your disappearance — you will have been missing exactly 18 months.

On Friday, February 15, last year you woke about ten minutes after we left the house to go to work.

You got ready for work, opened the curtains, made your bed and left the house at your usual time.

CCTV caught you walking, on your phone as usual. We know you sent Snapchat streaks to friends as always. And then you vanished.

Roughly 15 minutes after being captured on CCTV your phone was switched off and it has never been turned on or used in any way again.

That is when you vanished for real. No one has seen or heard from you since. No one has found any of your belongings.

That was my reality 18 months ago and is still the same today.

We have had so many acts of kindness. Random hugs from strangers, cards through the post, messages of support on social media, food parcels from friends.

One kind lady sent me a book from the US on coping strategies for grief and loss.

There have been many donations of money, first for the JustGiving page to raise funds for posters, then the Missing People charity and then for the Papyrus charity after the tragic loss of your brother Haydon.

Not to mention the two angelic donors of the reward money of £10,000 and the people who paid for posters on vans and trucks.

We are grateful for every act of kindness from every single person who has helped.

A lady from my estate dropped flowers and a card on my doorstep, letting me know that everyone is hoping for you to be found.

To believe that you ran away is a stretch of the imagination, because you were so happy at home.

We had been looking at wallpaper for your room and you wanted to buy a new bed. We were meant to be going on a two-week holiday that we were all looking forward to.

You had a good job with good pay and life was good for all of us.

Why would you walk away from everyone and everything you knew? You lived on your phone, the pictures you took at Haydon’s 21st are on there.

But your phone has not been turned on. Your bank account has not been used.

But, Leah, if you are out there somewhere and left us because you were upset about something, please, come home. Let us help sort it out.

There is nothing that is too big that cannot be fixed. We all miss you so much. All your family and friends are beyond worried about you.

It has been such a long time since I could give you a cuddle. I need to hear your laugh again.

I miss you telling me about your day at work. I miss the way you huff sometimes as you sit down.

I have washed your bed sheets and your dressing gown again. I’m off to dust your room after I’ve written this.

Everything is still there as you left it, waiting and ready for you.

Please come home for your 21st birthday Leah. I promise, for real this time, there is no surprise party.

But if the worst has happened and you cannot come home, this is my message to the person responsible: It may take time, but you will be caught.

You have destroyed my happy family. We will never heal from the needless and heinous pain you have caused.

You have taken a kind, naive young lady who had everything to look forward to and stopped her life in her prime.

You have robbed her family and friends of a caring, loving individual. You broke her brother, Haydon, mentally.

You have taken away grandchildren that we will never meet. Stopped two wedding days that we will never get the chance to plan.

To lose one child is the most horrendous experience in life, one you would not wish on your worst enemy.

To not know why that child is no longer with you, or even if they are OK is torturous.

To lose two children is soul-destroying.

I do not know how I get up every day. It takes a lot of willpower. It takes a lot of energy. Energy I usually do not possess.

I still feel numb. I still feel lost. Helpless. Useless. Close to tears all day. Angry.

People tell me I am amazing. I’m not. I’m just trying to do my best to survive this situation, be there for my family and get through each day and night so that I am still here for you, Leah, if by some miracle you should happen to come home.

If I fall apart and go crazy who will fight for answers? I need to hold it together for your dad John and sister Jade. They need me as much as I need them.

Leah, I am making an appeal on your behalf to anyone reading this letter, to please keep a look out for you.

It’s more difficult now people are wearing masks because of Covid but please try to look for Leah.

It was a busy time on the last day of school, the day after Valentine’s in 2019. A memorable day.

Did they see you Leah? Did they see something small that they may not think is important but could be an important clue?

Did they hear you scream or hear a noise that might help locate you?

No matter how insignificant the memory, I am asking witnesses to call the police if they have information that will help end our torment.

Your loving mum, Claire.

Meanwhile Claire's husband, Leah's dad John, said today in a poignant Facebook post: "Happy 21st birthday to our darling, beautiful Leah. We couldn't buy you a present because sadly you are not here with us today.

"So we got you centre page in the Sun newspaper and the biggest bunch of flowers in the shop instead. We love you so much and hope that you will come home soon. Everybody misses you like mad. "

IF ANYBODY HAS ANY INFORMATION AT ALL ABOUT LEAH PLEASE CALL POLICE ON 101 OR CRIMESTOPPERS ANONYMOUSLY ON 0800 555 111.