A cold-hearted thief is believed to have swiped a black handbag containing the sapphire and diamond-encrusted platinum band from a secluded village church in Sussex as Caroline Marshall, 32, and James Granshaw, 29, said their vows.
Distraught family members said the bride was left in floods of tears when she realised her beloved ring was missing following the service in Saturday afternoon.
They are desperately trying to track down the £6,000 ring, which they say has "priceless" sentimental value as it was lovingly hand-designed by her husband at an ethical London jewellers.
James' father Mervyn, a retired airline pilot from Guildford, said: "It is just appalling to do this to a bride on her wedding day.
"This was not a drive-by or a walk-by theft, someone has walked up to the church and targeted it. I just despair. To steal a bride's engagement ring from a church - how low can you go?
"It put a cloud over the whole day. They are totally heartbroken at what has happened. We are trying to reassure them, but Caroline has been in floods of tears on her honeymoon because she is so upset."
James, a qualified barrister and legal adviser at Waverley Borough Council, spent months painstakingly researching ethical jewellers to design an engagement ring that did not contain so-called 'blood diamonds' - which are mined in conflict zones - and only used ethical materials.
And he helped to design the "irreplaceable" ring himself.
After getting engaged on the snowy ski slopes in Switzerland in 2012, the couple and their family and friends gathered at the parish church of St Peter ad Vincula in Wisborough Green, West Sussex last Saturday for the nuptials.
But moments before the ceremony was due to start, Caroline, who works in compliance for an investment firm in the City of London, realised she still had her engagement ring on. She slipped it off her finger and gave it to her best friend and bridesmaid, who put it in her black LK Bennett handbag for safekeeping.
After the service they realised the ring was missing and called the police.
The stolen handbag also had an iphone in it, and the frantic couple were able to track the device for a couple of hours and saw it was making off towards Haywards Heath before the signal went dead that evening.
Caroline and James have jetted off for a two week honeymoon in the borders of Tuscany, Italy, but their family say the theft "blighted" what should have been the happiest day of their lives.
Mervyn, 60, said: "The bridesmaid feels so guilty - it is her best friend. My son and Caroline have gone on their honeymoon, but it has cast a huge shadow over the day.
"The engagement ring is unique. It is not worth £10 million, but it has huge sentimental value.
"James put in a lot of effort to create that ring because he knew she would appreciate it. They go to great lengths to make sure it is ethical. It is not some off the shelf ring, it took months of organisation and she loved it. Now it is gone."
The couple fear the thief intends to sell their prize possession to one of the dozens of famous jewellery shops in the Lanes in Brighton, and they are urging anyone who has any information about the ring to get in touch.
A Facebook page called 'Help us find the ring' has been set up to help the search and has received almost 200 likes, and friends and family are using the twitter hashtag carolinesring.
A spokesman for Sussex police was not immediately available to comment but the force have re-tweeted the appeal.
32岁的卡洛琳·马歇尔（ Caroline Marshall）和29岁的詹姆斯·格兰沙（James Granshaw）在苏塞克斯（Sussex）乡村的一家偏僻的教堂进行婚礼宣誓时，一个冷血的窃贼盗取了卡洛琳的黑色手袋，其中就有她的镶钻蓝宝石铂金戒指。
双方亲属都很烦乱，他们透露，星期六下午，新娘得知心爱的戒指丢失时不禁泪如泉涌。
大家都急切的想要追回这枚价值六千英镑的戒指，詹姆斯满怀爱意亲自在伦敦珠宝商处手工设计了这枚戒指，因此这枚戒指有“无价”的情感意义。
詹姆斯的父亲莫文（ Mervyn）是吉尔福德（Guildford）的退休飞行员，他说：“婚姻当天新娘丢了婚戒，这实在是太可怕了。”
“小偷不是路过这里顺手牵羊，而是以此为目标进教堂行窃的。我简直要绝望了。竟然在别人婚礼当天偷人家的订婚戒指，实在是太卑鄙了！
“我们一整天都愁云笼罩。事情发生时大家都很伤心。我们都努力安慰这对新人。但是蜜月期间，卡洛琳一直在不停地哭，因为她实在很伤心。”
詹姆斯是韦弗利镇理事会（ Waverley Borough Council）的挂牌律师和法律顾问，他花了好几个月努力钻研环保珠宝设计，终于设计出了这枚订婚戒指。戒面上并未镶嵌所谓的“血钻”——因为血钻需要在战争冲突爆发的地区开采——詹姆斯只使用来源正当的材料。
他自己设计了这枚“无可替代”的钻戒。
2012年，卡洛琳夫妇在瑞士的某个滑雪场举行了订婚仪式，上周六，他们又在西苏塞克斯郡，威斯布罗格格林市（Wisborough Green）的圣彼得维克拉（St Peter ad Vincula）教堂举行了婚礼，双方亲友均出席。
卡洛琳是伦敦一家投资公司的员工，在婚礼快开始前，她才发现自己还戴着订婚戒指，于是就把戒指摘了下来交给她最好的朋友和伴娘保管，后者便把戒指放进了她的黑色班尼特（LK Bennett）手袋里。
仪式结束后他们才发现戒指不见了，并报了警。
新娘遗失的手袋里还有一部苹果手机，这对夫妇现在无比焦急，运用设备对手机连续追逐了好几个小时，信号最终在海沃兹希思（Haywards Heath）方向消失。
卡洛琳和詹姆斯已搭乘飞机去度蜜月了，他们将在意大利托斯卡纳（Tuscany）边境处逗留两个星期，但是双方亲属却表示那个盗贼“摧毁了”本该属于这两人的一生中最幸福的时刻。
莫文今年六十岁了，他说“女傧相感到很愧疚——最好的朋友遭遇了这样的事。我儿子和卡洛琳已经出发去度蜜月了，但今天的事给我们每个人的心上都蒙上了巨大的阴影。”
“被偷的订婚戒指可谓独一无二。戒指并不值一千万英镑，但意义巨大。”
“詹姆斯花了很多心血，因为他知道卡洛琳一定会喜欢，他们花了很大的功夫，确保戒指材料的来源正当的。这可不是那种一买就能买到的货色，詹姆斯花了好几个月来设计样式，卡洛琳也很喜欢。现在它被偷了。”
新婚夫妇害怕盗贼会把这枚珍贵的戒指卖给某家著名的珠宝店，布莱顿(Brighton)的小巷子到处都是这种店，这对夫妇希望任何知情人士能与他们取得联络。
他们特地设了一个脸书主页“帮我们找戒指”，已收到约有两百个赞，亲友的推特上都加了“卡洛琳的戒指”这个标签。
苏塞克斯郡的警方发言人表示，警方虽不能立即破案，但有关部门也转发了相关推特消息。
