How do you prove to the insurer the value of the contents if you do not have receipts?

Well the clothes etc could be 2 or 3 years old.

What do the insure do for example if the items were worth Ł300 or more?

Thats a conversation for you to have with the insurance company. I take pictures of my luggage as I pack it so I know what there is and I don’t have expensive items and am sad enough to keep a spreadsheet of.my clothes including when/where purchased and item and a photograph of receipt or online order. In case if I need say another pair of trousers for a suit or want to buy more of those trousers.

Not sure this is best placed on the BA forum. However, I know from experience more expensive items, jewellery etc, a photo of you wearing helps.

Could be the case with expensive items of clothing...

I have experienced this before, and it essentially comes down to: no receipt, no reimbursement. Unfortunately, there is no middle ground in this matter. Without a valid receipt, it is not possible to process any reimbursement requests.

Sign up for your payment card app? On the Amex app, I can request statements going back for seven years. One way of showing a proof of payment.

Anybody can get a copy statement in the last 6 years under the GDPR regulations. A bank/card statement saying Selfridfes proves you spent Ł300 there not what you spent it on.

There is a bit of a game here, in that airlines are required to minimise their losses and have a suspicion that claimants over-egg their inventory of lost items. It is not a requirement to have a receipt to prove loss, and ultimately someone could take an airline to court to establish their claim, something airlines try to avoid. BA, on the whole, has not got a bad reputation in this area, mostly claims are met in full. There have been three historic posts in this BA forum where someone has - in my view - taken the mick, two were paid, one was not.

My advice would be after packing your bag, unpack it again after taking everything out over a table top, bed or floor and taking a photo. Then repack. This actually doesn't take long, the repack process will often give a better result anyway. This doesn't have to be every time one flies, since usually most people, most of the time, take very similar items. Not only does it help with claims - mainly in terms of not forgetting something in the claim - but it also helps with a future trip to prevent something from being forgotten. I do this from time to time as a HBO traveller, that isn't a complete immunity here, if you end up on a smaller aircraft or even a full Embraer 195, but for checked luggage it is a quick and easy way to keep on top of matters.

Thanks for all the advice all.

To add to this, make sure you email yourself the photos (especially as close as possible to your flight date). This gives a timestamp of when you had the items in your possession.

This is also helpful for any valuables as it can provide you with ammo if immigration decides you should pay duty on that expensive necklace or ring or laptop (as likely or unlikely as it can be) that you might be wearing/carrying with you.