To ask how on earth people pack light?!

I agree @NeedSomeAnswersPlease that list is fine tho I’d lose the spare trainers, you don’t need them.

If you do that, what is stopping it fitting?

This sounds like a totally legit packing list and I really think that will fit fine in an overhead carry on case?

I should have added, last trip I used that backpack for was a trip to the Isle of Man TT for a couple of nights and that's all I took.

It easily fitted a couple of days of outfits and essentials and I could also use it during the day for our trips to the races.

I only read through OP's posts so I apologise if this ha been covered by others.
@NeedSomeAnswersPlease you are going for 4 days and are staying in AirBnB (which will 100% have a washing machine for emergencies as well as a hairdryer). The weather is variable and you need to prepare for both sunny/hot and rainy cooler days. You are taking a pair of comfy shoes and want a change for the evening. You will be wearing team shirts for at least two days of the holiday but want a change of clothes for the evening. Did I get it all right?
So, you need:
Day 1. Team shirt + bottoms + comfy shoes
Evening 1. An outfit you can dress up or down depending on evening activities + alternative shoes
Day and Evening 2 as above
Day 3 an outfit for day activities
Evening 3 as E1
Day and Evening 4 as above

Therefore, you need 2 team t-shirts, 2 pairs of bottoms, 2-3 evening outfits, 2 daytime outfits. 3 pairs of shoes (comfy, cool weather, hot weather). A cardigan and a waterproof.
So this could be: 2 t-shirts, 4 pairs of bottoms, 2 casual tops, 2 fancy tops
Or
2 t-shirts, 4 bottoms, 2 casual tops, 3 dresses

As a minimal traveler I could do that trip with 2 team shirts, two pairs of shorts, a dress, two tops to go with the bottoms, a pair of flat sandals and pumps for an evening out and a cardigan. I would travel in a pair of nice jeans, trainers, a nice shirt and waterproof jacket. I can do it in a Ryanair shitty baggage allowance and still have space to pack my ipad and toiletries.

ETA: obviously I left out 4 sets of underwear and socks, assuming it is given.

With BA, the additional item you can take is pretty large.

I have one of these and, as long as you don't ram it completely full, it fits the additional item size.

https://www.amazon.co.uk/dp/B0CTH5NG89?ref=ppx_yo2ov_dt_b_product_details&th=1

You can get enough in there alone for a trip, never mind with the cabin bag you're also taking!

OP, you've spawned a new Mumsnet phenomenon: the competitive underpacking thread!

Mooncup.

Figure out what you can buy there.

Wear multiple layers of clothes on the plane and ones with lots of pockets.

Put on all the jewel you're taking.

Cameras and books you can carry arent included.

Only take the shoes you wear on the plane.

For all those that keep suggesting it- OP is staying in an Airbnb, so no toiletries or hairdryer in the hotel.

OP, I honestly think that you are either capable of packing light or you're not. I am quite good at it, my best friend is constantly in awe that I can take a cabin suitcase for a full week away- but she simply has a lot of clothes and loves to have lots of options. She wouldn't want to pack light even if she could, she's just not that person.

It's too late now I know but your mistake was ever thinking you'd be able to be that person. In future, just accept this about yourself, book the check in luggage and plan your trains accordingly!

For now, packing cubes are definitely my secret- I can pack about twice as much with them than without them- I know you say they don't work for you, can I ask how you're using them? Are you rolling everything up tightly?

I always snigger at the airport when I see people with massive suitcases for a weeks holiday.

Personally I CBA carrying it and then having to unpack it / put it away (unused when you return).

If you are an over packer - ask yourself why?

Is it anxiety? Preparing for the unexpected and the feeling of losing control when leaving home.

Comfort - finding comfort in bringing more than they need.

Coping - overpacking helps people cope with distance from home or emotions from stressful situations.

After years of business travel I always travel very light (hand luggage for a week, I’m off to Asia for a month soon and will travel with just one small medium size check in).

My top tips:

Mini size / decant toiletries into travel bottles and the absolute minimum only. You don’t need shower gel (it’s in the hotel), serums, face masks etc.

You don’t need a hair dryer (it’s in the hotel) or straighteners etc. You can go without for a week.

You don’t need a different outfit every day. Plan plan plan what you are going to wear and make sure you can mix & match things.

Shoes take up a huge amount of room - so be really ruthless.

I am definitely not a light packer (I am a nightmare for taking stuff "just in case") but I have a Kipling duffle bag that is like a tardis that I can get up to 8 days worth of stuff in and then habe a small backpack with my cosmetics bag and day stuff.

I recently paid more for hold baggage on a 7 day trip to the USA and then saw on the flight that most people's "hand luggage" was bigger than my hold luggage😁

Where I do free up room is shoes - on recent 8 day trip to France I just wore birkenstocks and took no other shoes and for the afrementioned US trip I wore trainers on the flight and just packed a pair of metallic supergas for smarter and light ballet flats for the evening. No heels.

I also don't take a hair drier etc.. and pack v light on the make up and use the soap and body wash provided by the hotel.

Several posts including your follow ups landed while l was typing, otherwise l would have added a little more.

Unless you are really staying at the back of beyond, most well known brands should be available locally. Likewise toiletries.

With Shampoos and Conditioners, a different shampoo should make minimal difference . It stays on your head for minutes and is washed away. Conditioner is different because after rinsing, it is designed to remain in your hair.

lf you really think this is going to ruin your trip though, you can add hold luggage to your booking now. Beware though, l’ve had hold luggage lost twice, which is why I prefer to have it in the cabin with me.

What does going to a Grand Prix actually involve?

Mainly standing/sitting around surely.

Part of this depends who you are flying with. Carry on allowances vary greatly, even when bag sizes are similar. For example BA have a max of 23 Kg plus a small handbag/rucksack.

l’m not quite sure why you need to take much extra “bits” for your period. Is the difference not minimal? Remember Tampax etc can be bought locally on arrival.

Tee shirts and tops take up minimal space. You can also wash things through.

My clothes and shoes are not that excessive. I just seem to have a lot of 'stuff'.
Hair products
Hairdryer because I never like the hotel ones
Hair brushes to style my hair
Power banks
Sunglasses
Loads of medication

All my 'stuff' takes the space of a bag all by itself

I could buy shampoo and body wash there but I use special shampoo for grey hair and SPF for my face that I can't get in many places. Even if I didn't bring them, the other stuff is still a bag full

For the dressing gown lovers out there, bring a beach cover up, you know, those very light gossamer type things and use that. They fold into nothing.

Another tip for travelling light is to go with a bloke.

They take damn all, so you can fit a lot of your stuff in THEIR bag. I do this all the time if not travelling alone. If going alone, it's minimal and I re-wear a lot of clothes. Only you will know, believe me.