Baby, you can drive my car - keys to love success revealed

Planning a holiday, driving each other's cars and having a key to your partner's flat have been hailed as signs a relationship is 'serious', a new survey has revealed.

Researchers quizzed 2,000 people to reveal the top 50 things which indicate a couple are past the 'seeing each other' phase of a relationship.

Posting a 'loved-up' photo on Facebook, changing your status to 'in a relationship' and being introduced to wider friendships circles also show couples are the 'real deal.'

While meeting potential in-laws, staying overnight and divulging salary details also show trust and growing love for a partner.

And couples are usually together for just over five months before they deem the relationship to be 'serious'. A spokesman for Monarch Airlines, which commissioned the study said: "Dating is a minefield at the best of times. But one of the most confusing and stressful parts is deciding firstly when you are both comfortable saying you are boyfriend and girlfriend, and then secondly, when that partnership has reached the next level. As this survey demonstrates, there are loads of factors which couples take into account before deciding whether their relationship is serious or not. It's no longer just a case of talking about moving in together, marriage and children. There are smaller elements such as when to say I love you, when to stay the night, and when to swap house keys.

"And there are other acts which can show real commitment such as agreeing to spend a week away together or attending family gatherings. We are pleased to see that taking a holiday together is the third most popular sign that your relationship is getting serious. People travel for lots of different reasons but spending time together is one of the most popular."

The study also highlighted that couples deem a relationship as more serious when they get more comfortable – which means showering together, lounging around in pyjamas or discussing intimate health issues.